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MOTOR  VEHICLES 

and    THEIR    ENGINES 

A  Practical  Handbook  on  the 
CARE,  REPAIR  and  MANAGEMENT 

OF 

MOTOR  TRUCKS  and  AUTOMOBILES 

for  Owners,   Chauffeurs,   Garagemen  and  Schools 
BY 

EDWARD  S.   ERASER 

American  Bosch  Magneto  Corporation;  Formerly,  Captain,  C.  A.,  U.  S.  A. 
Instructor  Motor  Transportation  Course,  Coast  Artillery  School 

AND 

RALPH  B.  JONES 

Willys  Overland  Company;  Formerly,  Captain  C.  A.,  U.  S.  A. 
Instructor  Motor  TradspgostatiQn,  Qpurse,  Coas,t,  Artillery  School 


278  ILLUSTRATIONS 


NEW  YORK 

D.  VAN  NOSTRAND  COMPANY 

EIGHT  WARREN  STREET 

1921 


•P? 


Copyright  1919,  by 
D.  VAN  NOSTRAND  COMPANY 


Printed  in  the  U.  S.  A. 


PREFACE 


The  following  pages  represent  the  result  of  an  attempt  to  collect 
in  a  comparatively  small  book  such  elementary,  theoretical,  and 
practical  information  as  will  assist  in  the  operation,  upkeep,  and 
adjustment  of  the  motor  vehicles.  This  book  was  written  with  a 
three-fold  purpose;  as  a  guide  for  the  personal  instruction  of  the  car 
owner,  as  a  hand  book  for  chauffeurs,  garages,  and  repairmen,  and  as 
a  text  book  for  Automobile  Schools.  The  simplest  language  has  been 
used  and  technicalities  have  been  reduced  to  a  minimum.  The 
fundamentals  of  gas  motor  operation,  as  well  as  the  care  and  opera- 
tion of  the  principal  accessories  of  the  motor  vehicles  concerned,  are 
discussed  in  detail  and  at  greater  length  than  is  the  usual  practice. 

To'  obtain  the  maximum  economy,  efficiency,  and  life  of  the 
apparatus  the  last  four  chapters  of  the  book  should  be  studied. 
These  chapters  are  the  result  of  the  authors'  observations  and  expe- 
rience with  the  great  number  of  trucks,  tractors,  automobiles,  and 
motor-cycles  operating  under  their  supervision. 

This  book  is  the  outgrowth  of  the  authors'  former  volume  "  Motor 
Transportation  for  Heavy  Artillery,"  which  was  prepared  for  use  as 
a  textbook  in  the  Coast  Artillery  School's  course  in  the  subject. 
The  valuable  experience  gained  in  connection  with  their  work  as 
instructors  in  this  school  has  been  embodied  in  this  second  edition  so 
that  the  book  contains  all  the  information  necessary  to  properly 
operate  and  care  for  motor  vehicles. 

The  authors  wish  to  express  their  indebtedness  to  the  Norman 
W.  Henley  Publishing  Company  for  permission  to  use  figures  6,  7, 
46,  136,  215,  237,  246,  252,  260,  262,  263,  266  and  268  from  Page's 
"  Modern  Gasolene  Automobile." 

April,  1920.  THE  AUTHORS. 


CONTENTS 


CHAPTER  PAGE 

\          I  THE  GAS  ENGINE 1 

i-      II  PRINCIPLES  OF  Two  AND  FOUK-CYCLE  ENGINES 8 

((    III  TIMING 14 

IV  ENGINE  BALANCE  AND  FIRING  ORDER 21 

V  COOLING  SYSTEMS 34 

VI  FUEL  FEED  SYSTEMS 48 

VII  FUELS 55 

VIII  ELEMENTS  OF  CARBURETION 63 

IX  CARBURETORS 72 

X  CARBURETORS  (Continued) 89 

XI  PUDDLE  TYPE  CARBURETORS 114 

XII  MAGNETISM 117 

XIII  ELEMENTARY  ELECTRICITY 128 

XIV  BATTERIES 135 

XV  INDUCTION 146 

XVI  BATTERY  IGNITION  SYSTEMS 151 

XVII  MAGNETOS:  ARMATURE  TYPE 172 

XVIII  MAGNETOS:  ROTOR  TYPE 193 

-S  XIX  DUAL  AND  DUPLEX  IGNITION  SYSTEMS 201 

XX  STARTING  AND  LIGHTING  SYSTEMS 207 

XXI  POWER  TRANSMISSION 227 

XXII  CLUTCHES 232 

XXIII  TRANSMISSIONS 241 

XXIV  DRIVES 258 

XXV  DIFFERENTIALS 263 

XXVI  RUNNING  GEAR 270 

XXVII  TIRES  AND  RIMS 289 

XXVIII  How  TO  DRIVE 299 

XXIX  ENGINE  TROUBLES  EXPERIENCED  ON  THE  ROAD 303 

XXX  LUBRICATION 309 

XXXI  CARE  AND  ADJUSTMENT.  .  317-ltf-l^ 

3T3-<* 

XXXII  CARE  AND  ADJUSTMENT  TABLES 329 

INDEX .345 


MOTOR  VEHICLES 

AND  THEIR  ENGINES 


CHAPTER  I 


THE  GAS  ENGINE  M  - *'-  - '' • 

The  term  "Gas  Engine"  is  commonly  used  to  designate  all  types 
of  internal  combustion  engines  regardless  of  whether  they  operate 
on  gas  or  liquid  fuel.  Liquid  fuel  is  almost  universally  used  in 
engines  adapted  for  motor  transportation.  GasolirTe  is  the  most 
commonly  used  liquid  fuel.  Kerosene,  alcohol,  benzol,  and  fuel  oil 
are  used  in  internal  combustion  engines,  but  in  general  their  use  is 
confined  to  engines  of  the  stationary  type. 

In  the  internal  combustion  engine,  the  fuel  is  introduced  into  the 
cylinder  in  a  combustible  mixture  and  is  there  ignited.  This  type 
of  engine  is  divided  into  two  classes,  that  in  which  the  combustion 
takes  place  gradually  and  that  in  which  the  combustion  takes  place 
almost  instantaneously. 

The  Diesel  engine  comes  under  the  class  in  which  the  combustion 
is  gradual.  The  liquid  fuel  is  gradually  injected  into  the  cylinder 
which  contains  only  air  under  high  pressure.  This  air  is  compressed 
to  such  a  degree  that  a  temperature  far  above  the  ignition  point  of 
the  fuel  is  obtained.  This  causes  the  fuel  to  ignite  as  it  is  injected 
into  the  combustion  space.  Complete  but  gradual  combustion  is 
obtained  in  this  manner.  Engines  of  this  type  are  not  applicable 
for  motor  propelled  vehicles,  largely  because  of  their  lack  of  flexibility. 

In  the  gasoline  engine  the  fuel  is  burned  almost  instantaneously. 
The  air  is  mixed  with  the  fuel  outside  of  the  combustion  space  (Fig.  1) 
and  the  resulting  combustible  mixture  is  drawn  into  the  cylinder 
where  it  is  ignited  under  compression  by  some  outside  source  of  heat., 
the  electric  spark  being  the  one  universally  adopted. 

Combustion  or  burning  is  always  accompanied  by  the  production 
of  heat.  The  temperature  produced  depends  upon  the  rapidity  and 
completeness  of  the  combustion.  The  faster  the  burning  the  higher 
the  maximum  temperature  produced.  A  slow  burning  fuel  produces 
a  more  uniform  temperature,  but  not  as  high  as  is  produced  by  a 
fuel  burning  almost  instantaneously. 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


CRAM  SHAFT  BMniNG- 
CflAflK  MSF     ^£»HMJrmr£  CAn 
fWMSI  CM  SHAFT  GEM 


Fig.  1 — Engine  Parts 


WORKING  PARTS: 
Pistons 

Piston  rings 

Wrist  pins 
Connecting  rods 

Connecting  rod  caps 

Shims 

Connecting  rod  bearings 
Crank  shaft 

Gear  to  cam  shaft 

Crank  arms 

Crank  pins 

Journal 

Fly  wheel 


VALVE  MECHANISM: 

Cam  shaft 

Cam  shaft  gears 

Inlet  cams 

Exhaust  cams 
Push  rods  (lifter  rods  or  tappets) 

Roller  or  mushroom  head 

Adjusting  nuts 
Valves 

Valve  stem 

Valve  spring 

Valve  head 

Valve  clearance 


ENGINE  NOMENCLATURE 


Fan  Support  »» 
Fun  tfl«<le<i 


Oil  Wvll<SsF^  _  fi  / 

•~<MT»~»-£r  ^^Or^n^ 


Fig.  2 — Sectional  View  of  Typical  Four-Stroke  Cycle,  Four-Cylinder 

Motor  Truck  Engine,  Showing  Important  Internal  Parts 

and  Their  Relation  to  Each  Other 


STATIONARY  PARTS 

Cylinder  casting 

Water  jacket 

Inlet  ports 

Exhaust  ports 

Valve  seats 

Cylinder  head 

Combustion  space 
Crank  case 

Upper  half 

Lower  half 

Lifter  guides 

Main  bearings 

Cam  shaft  bearings 

Oil  reservoir 

Oil  pump 

Float 

Gear  cover 

Breather  tube 


ACCESSORIES: 
Inlet  manifold 
Exhaust  manifold 
Fan  assembly 

Fan 

Pulley 

Belt 

Bracket 
Starting  crank 
Valve  caps 
Spark  plugs 

Compression  cocks  (priming  cocks) 
Water  pumps 

Magneto  or  timer-distributor 
Carburetor 


4  MOTOR  VEHICLES  AND  THEIR  ENGINES 

When  gases  and  most  metals  are  heated  they  expand,  some  ex- 
panding more  than  others.  Gases  expand  more  than  metals  for  a 
given  amount  of  heat.  A  definite  increase  of  temperature  will  cause 
a  gas  to  expand  a  certain  amount  and  as  the  heat  is  increased  the 
expansion  increases  in  proportion.  When  the  mixture  in  the  cylinder 
is  burned,  the  resulting  heat  causes  the  gases  to  expand,  the  amount 
of  this  expansion  depending  upon  the  temperature. 

When  a  gas  contained  in  a  closed  vessel  is  heated  its  expansion 
exerts  a  pressure  equally  in  all  directions.  This  condition  exists  in 
the  cylinder  of  an  internal  combustion  engine  after  combustion  has 
taken  place.  The  resulting  pressure  is  exerted  on  the  cylinder  walls 
and  piston.  The  piston,  being  movable,  under  the  force  of  the 
expanding  gases,  moves  outward  to  the  full  limit  of  its  stroke. 

The  energy  resulting  from  this  expansion  must  now  be  trans- 
formed into  useful  work.  In  order  to  accomplish  this,  a  construction 
such  as  shown  in  Fig.  3  is  used. 

The  force  exerted  on  the  piston  "K"  is  transmitted  through  the 
connecting  rod  "E"  to  the  crank  shaft  UH"  which  is  made  to  revolve, 
turning  through  one-half  of  a  revolution  as  the  piston  moves  out- 
ward. Attached  to  the  crank  shaft  is  a  fly  wheel,  which  stores  up 
energy  and  its  momentum  carries  the  piston  through  the  balance  of 
its  motion  until  it  receives  another  power  impulse.  In  this  way  the 
reciprocating  motion  of  the  piston  is  transformed  into  a  rotary 
motion  at  the  crank  shaft. 

The  operation  of  the  gasoline  engine,  as  already  shown,  depends 
upon  the  production  of  heat  in  the  cylinder  caused  by  burning  the 


Fig.  3— Engine  Operation 


THE  GAS  ENGINE 


.EXHAUST  GAS, 
DIRECT  RADIATION 

35.6% 


POWEHOF  CAR 

12.5% 


EXCESS  POWER  FOR 
ACCELERATION.  HILLS.  ETC. 

5-4% 


FRONT  WHEEL* 

0.6% 


AIR  RESISTANCE 
7.1% 


Fig.  4 — Energy  Diagram 


6  MOTOR  VEHICLES  AND  THEIR  ENGINES 

fuel.  A  given  amount  of  fuel  will  produce  a  certain  amount  of  heat 
when  completely  burned.  However,  the  total  heat  value  of  the  fuel 
cannot  be  utilized  because  there  are  certain  losses  which  must  always 
occur  even  in  the  best  designed  engine.  Badly  worn  engines,  im- 
perfect carburetion,  and  faulty  ignition  will  add  to  the  necessary 
losses  and  decrease  the  percentage  of  energy  actually  available  for 
useful  work. 

The  highest  thermal  efficiency  attained  in  the  best  types  of  large 
stationary  internal  combustion  engines  (Diesel)  is  about  35%  while 
few  automobile  engines  ever  exceed  20%.  The  diagram  (Fig.  4) 
shows  the  dispersion  of  energy  from  fuel  as  it  passes  through  the 
engine  of  a  high  class  touring  car  traveling  at  a  speed  of  40  miles 
per  hour  on  direct  drive. 

Referring  to  Fig.  4,  it  will  be  seen  that  a  certain  amount  of  the 
heat  is  absorbed  by  the  cooling  system.  Also  a  considerable  amount 
of  heat  is  lost  in  the  exhaust  gases.  Nearly  70%  of  the  total  fuel 
value  is  lost  in  this  way  and  this  loss  cannot  be  materially  reduced 
below  this  amount.  The  loss  due  to  engine  friction  will  vary  con- 
siderably with  the  design  and  condition  of  the  engine.  The  point 
indicated  as  "  Motor  Full  Power"  represents  the  amount  of  energy 
remaining  for  useful  work.  When  this  energy  is  applied  to  driving 
an  automobile,  it  is  consumed  as  shown  in  the  diagram.  This  leaves 
but  a  small  amount  of  reserve  energy,  which  will  be  decreased  as  the 
speed  of  the  machine  is  increased.  Every  design  of  engine  and  car 
of  course  has  a  different  energy  diagram  corresponding  to  the  degree 
of  efficiency  attained  at  different  speed  and  loads. 

Engines  of  all  kinds  are  rated  in  horse-power — the  measure  of 
the  rate  at  which  they  can  do  work.  One  horse-power  represents 
33,000  foot-pounds  of  work  per  minute.  There  are  two  ways  of 
measuring  engine  power.  The  power  developed  by  the  expansion 
of  the  gases  in  the  cylinder  can  be  determined,  in  which  case  the 
INDICATED  HORSE-POWER  is  obtained.  By  means  of  a  Prony 
Brake  or  Dynamometer,  the  power  which  the  engine  actually  delivers 
can  be  measured  and  this  is  called  the  BRAKE  HORSE-POWER. 
The  brake  horse-power  of  an  automobile  engine  will  usually  be  from 
70%  to  85%  of  its  indicated  horse-power,  the  losses  being  energy 
consumed  in  friction  and  other  causes  in  the  engine  mechanism. 
However,  in  obtaining  the  horse-power  of  an  engine,  formulae  are 
used  based  on  the  indicated  horse-power  assuming  certain  standard 
conditions.  The  horse-power  obtained  in  this  manner  is  often  incon- 
sistent with  the  actual  horse-power  developed  on  test. 

There  are  a  number  of  quick  rules  for  estimating  the  power  of 
engines  according  to  their  cylinder  dimensions  and  the  piston  speed. 


THE  GAS  ENGINE 

* 

The  one  most  used  for  four-cycle  engines  is  given  below.    The 
simplest  formula  is  that  of  the  Society  of  Automobile  Engineers: 


.. 

2.5 
The  formula  for  finding  the  indicated  horse-power  of  an  engine  is  : 

I.  H.  P.  (for  1  Cylinder)  =  R  A'  S' 

33,000x4 

Where  P  =  mean  effective  pressure  in  pounds  per  square  inch. 
A  =  piston  area  in  square  inches. 
S  =  piston  speed  in  feet  per  minute. 

Where  the  engine  has  more  than  one  cylinder,  the  result  ob- 
tained from  this  formula  must  be  multiplied  by  the  number  of 
cylinders.  The  brake  horse-power  is  obtained  by  multiplying  by  the 
mechanical  efficiency  of  the  engine.  The  complete  equation  for 
brake  horse-power  is: 

BHp=P.A.S.N.E. 

33,000  x  4 

Where  N  ==  number  of  cylinders. 
E  =  mechanical  efficiency. 

Assuming  a  mean  effective  pressure  of  90  pounds  per  square  inch, 
a  piston  speed  of  1,000  feet  per  minute,  and  a  mechanical  efficiency 
of  75%  and  substituting  these  values  in  the  formula  for  brake 
horse-power,  the  following  value  is  obtained: 

D2N  D2N 

B.  H.  P.  =  -  or  approximately  - 
2.489  2.5 

Where  D  =  diameter  of  piston  in  inches. 

This  is  the  S.  A.  E.  formula  for  four-cycle  engines 

For  two-cycle  engines  this  becomes: 


1.5 


CHAPTER  II 


PRINCIPLES  OF  TWO  AND  FOUR-CYCLE  ENGINES 

In  order  that  the  operation  of  the  gas  engine  be  continuous,  a 
certain  series  of  events  called  the  cycle  must  take  place  which  are 
repeated  over  and  over  in  the  same  regular  order.  In  order  to  clearly 
understand  the  events  that  compose  the  cycle  of  an  engine,  its  opera- 
tion will  be  compared  to  the  operation  of  the  old  style  muzzle-loading 
cannon,  which  is  the  simplest  form  of  internal  combustion  engine. 

Referring  to  Fig.  5,  the  first  step  necessary  to  fire  the  cannon  is 
inserting  the  charge;  the  corresponding  step  in  the  gas  engine  is  the 
ADMISSION  of  the  charge.  The  second  step  is  ramming  the  pro- 
jectile and  powder;  the  corresponding  step  in  the  gas  engine  is  the 
COMPRESSION  of  the  charge.  The  third  step  is  lighting  the  fuse; 
the  corresponding  step  in  the  gas  engine  is  the  IGNITION  of  the 
charge.  The  fourth  step  is  burning  the  powder  and  the  fifth  step 
expansion  of  the  gases  of  combustion  due  to  the  heat  produced  which 
forces  the  projectile  out  of  the  cannon.  The  corresponding  steps  in 
the  gas  engine  are  the  COMBUSTION  of  the  charge  and  EXPAN- 
SION of  the  gases.  The  sixth  step  in  the  operation  of  the  cannon  is 
the  escape  of  the  burned  gases  after  the  projectile  has  left  the  muzzle; 
the  corresponding  step  in  the  gas  engine  is  the  subsequent  EXHAUST 
of  the  products  of  combustion.  The  cannon  is  now  ready  to  be  fired 
again  and  the  engine  to  continue  its  operation. 

The  steps  comprising  the  cycle  of  operation  of  the  gas  engine  may 
be  summarized  as  follows : 

1.  Admission  of  the  charge. 

2.  Compression  of  the  charge. 

3.  Ignition  of  the  charge. 

4.  Combustion  of  the  charge. 

5.  Expansion  of  the  gases. 

6.  Exhaust  of  the  gases. 

In  the  operation  of  a  gas  engine  the  number  of  strokes  required 
to  complete  the  cycle  varies  with  the  type  of  engine.  In  the  type 
almost  universally  used  for  motor  vehicles  the  cycle  is  extended 
through  four  strokes  of  the  piston  or  two  revolutions  of  the  crank 
shaft  and  is  therefore  called  a  four-cycle  engine.  In  a  few  instances 
the  cycle  is  completed  in  two  strokes  of  the  piston  or  one  revolution 
of  the  crank  shaft  and  is  therefore  called  a  two-cycle  engine. 


B 


D 


Fig.  5 — Operation  of  Cannon  and  Engine  Compared 

0 


10  MOTOR  VEHICLES  AND  THEIR  ENGINES 

FOUR-CYCLE  ENGINES 

In  the  four-cycle  engine,  the  four  strokes  are  named  suction, 
compression,  power,  and  exhaust  in  accordance  with  the  operations 
of  the  cycle  which  occur  during  each  particular  stroke. 

SUCTION  STROKE.— During  this  stroke  (Fig.  5-A)  the  piston 
is  moved  outward  by  the  crank  shaft  which  is  either  revolved  by  the 
momentum  of  the  fly  wheel  or  some  external  starting  force.  This 
movement  of  the  piston  increases  the  size  of  the  combustion  space, 
thereby  reducing  the  pressure  in  it  and  the  higher  pressure  of  the 
atmosphere  outside,  forces  fresh  mixture  into  the  combustion  space 
through  the  open  inlet  valve. 

COMPRESSION  STROKE.— The  compression,  ignition,  and 
most  of  the  combustion  of  the  charge  takes  place  during  the  next 
inward  stroke  of  the  piston.  The  time  elapsed  between  the  mixing 
of  the  liquid  gasoline  and  air  and  its  admission  into  the  cylinder  is 
too  brief  to  secure  a  perfect  combustible  mixture.  What  passes 
into  the  cylinder  consists  of  air,  liquid  gasoline,  and  a  more  or  less 
perfect  mixture  of  the  two.  The  combustion  of  this  mixture  would 
be  slow  and  incomplete  resulting  in  a  loss  of  power  and  a  waste  of 
fuel.  In  order  to  obtain  a  homogeneous  mixture,  advantage  is  taken 
of  the  heat  produced  by  compression.  This  renders  the  gasoline 
more  volatile,  while  the  compression  forces  it  into  intimate  combina- 
tion with  the  air.  Even  then  a  perfect  mixture  may  not  result  for 
the  air  and  gasoline  vapor  instead  of  being  thoroughly  combined  may 
be  in  layers.  The  combustion  will  then  be  slow  and  uneven.  When 
the  mixture  of  air  and  gasoline  vapor  are  properly  proportioned,  this 
difficulty  is  seldom  encountered.  The  mixture  is  ignited  while 
under  compression  and  combustion  is  practically  completed  at  top 
dead  center. 

POWER  STROKE.— The  expansion  of  the  gases  due  to  the  heat 
of  combustion  exerts  a  pressure  in  the  cylinder  and  on  the  piston. 
Under  this  impulse  it  moves  outward. 

EXHAUST  STROKE.— When  the  exhaust  valve  is  opened,  the 
greater  part  of  the  burned  gases  escape  due  to  their  own  expansion. 
The  inward  movement  of  the  piston  pushes  the  remaining  gases  out 
of  the  open  exhaust  valve.  The  space  between  the  cylinder  head 
and  the  piston,  when  it  is  at  its  inmost  point,  is  called  the  clearance 
and  will  be  filled  with  the  remaining  exhaust  gases.  These  will 
dilute  the  fresh  incoming  charge. 

Thus  it  is  seen  that  in  this  type  of  engine  four  strokes  of  the  piston 
are  required  to  complete  the  cycle. 


PRINCIPLES  OF  TWO  AND  FOUR-CYCLE  ENGINES  11 


Fig.  6 — Three-Port  Two-Cycle  Engine 


TWO-CYCLE  ENGINES 

The  two-cycle  type  of  gasoline  engine  differs  from  the  four-cycle 
type  just  described  in  that  the  six  events  composing  the  cycle  are 
performed  during  two  strokes  of  the  piston  or  one  revolution  of  the 
crank  shaft.  Power  is  developed  during  every  outward  stroke  of 
the  piston  instead  of  alternate  outward  strokes. 

In  order  that  this  result  may  be  attained,  the  construction  of  the 
engine  is  changed.  As  shown  in  Fig.  6,  the  crank  case  is  utilized  as 
a  receiver  for  the  mixture  before  it  passes  to  the  combustion  space. 
The  valves  are  replaced  by  ports,  which  are  openings  into  the  com- 
bustion space.  These  are  covered  and  uncovered  by  the  piston  as 
it  slides  in  the  cylinder.  The  gas  inlet  port  to  the  crank  case  is 
uncovered  when  the  piston  is  at  the  inmost  point  of  its  stroke  ad- 
mitting the  mixture  to  the  crank  case.  This  is  air  tight  and  must 
have  a  separate  compartment  for  each  cylinder.  The  exhaust  port 
and  the  intake  port  are  uncovered  when  the  piston  is  at  the  outmost 
point  of  its  stroke.  The  exhaust  port  opens  first,  which  permits  the 
burned  gases  to  escape  after  combustion  has  taken  place.  The  intake 
port  opens  shortly  after  the  opening  of  the  exhaust  port  and  permits 
a  fresh  charge  to  pass  from  the  crank  case  to  the  combustion  space. 

During  an  inward  stroke,  the  pressure  in  the  crank  case  is  reduced 
as  the  piston  moves  inward  and  a  fresh  mixture  is  forced  into  it  by 
the  higher  atmospheric  pressure  as  soon  as  the  gas  inlet  is  uncovered. 
This  port  is  covered  when  the  piston  makes  an  outward  stroke  and 
the  mixture,  not  being  able  to  escape,  is  compressed.  The  tendency 


12 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


of  the  gas  to  expand  causes  it  to  flow  to  the  combustion  space  when 
the  inlet  port  is  uncovered,  and  in  entering,  it  strikes  a  deflecting 
plate  on  the  piston.  This  deflects  it  to  the  top  of  the  combustion 
space  instead  of  allowing  it  to  rush  across  the  cylinder  and  out  the 
open  exhaust  port.  The  inward  stroke  of  the  piston  covers  these 
two  ports  and  compresses  the  mixture,  ignition  occurring  in  the 
regular  manner.  The  pressure  developed  by  the  combustion  drives 
the  piston  outward.  As  soon  as  the  exhaust  port  is  uncovered, 
which  is  slightly  before  the  uncovering  of  the  inlet  port,  the  gases, 
which  are  still  expanding,  begin  to  escape.  They  are  further  expelled 
by  the  fresh  charge  that  enters  and  drives  them  before  it.  Thus  the 
six  events  of  the  cycle  are  performed  during  an  inward  and  an  out- 


Fig.  7 — Two-Port  Two-Cycle  Engine 


ward  stroke  of  the  piston.  On  the  lower  side  of  the  piston  a  charge 
of  fresh  mixture  is  drawn  into  the  crank  case  and  forced  into  the 
combustion  space  where  it  is  compressed,  ignited,  and  burned. 

The  type  of  engine  just  explained  is  known  as  the  three-port 
construction  of  two-cycle  engine.  There  is  also  a  two-port  construc- 
tion of  two-cycle  engine.  This  type  of  engine  differs  from  the  three 
port  in  that  the  inlet  port  to  the  crank  case  is  replaced  by  a  check 
valve  as  shown  in  Fig.  7.  When  the  pressure  in  the  crank  case  is 
reduced  due  to  the  piston  moving  inward,  the  higher  atmospheric 
pressure  opens  the  valve  and  forces  a  fresh  mixture  into  the  crank 
case.  The  valve  is  closed  by  the  action  of  the  spring  at  all  other 
times  and  is  further  assisted  in  closing  by  compression  in  the  crank 


PRINCIPLES  OF  TWO  AND  FOUR-CYCLE  ENGINES  13 

case.  The  operation  of  this  engine  is  identical  in  all  other  respects 
with  the  three-port  construction. 

In  all  two-cycle  engines  a  screen  is  placed  in  the  bypass.  The 
object  of  this  is  to  prevent  any  possibility  of  the  incoming  charge 
being  ignited  by  the  exhaust  gases  thus  causing  a  back  fire  into  the 
crank  case. 

At  slow  speeds,  two-cycle  engines  have  advantages  over  the  four- 
cycle in  having  a  power  impulse  every  revolution  of  the  crank  shaft 
and  in  not  having  valves  and  valve  mechanism  with  their  weight  and 
possibility  of  giving  trouble.  This  simplicity  makes  the  two-cycle 
engine  popular  for  motor  boats,  where  slow  and  constant  speeds  are 
desired.  For  higher  and  changing  speeds  these  advantages  are  out- 
weighed by  disadvantages  that  show  little  sign  of  being  overcome. 

With  the  engine  running  at  high  speed,  the  ports  are  open  for 
only  a  brief  period  during  each  stroke,  and  the  faster  the  engine  runs, 
the  shorter  will  be  the  period  during  which  the  gases  may  enter  or 
leave  the  combustion  space.  The  inefficiency  of  two-cycle  engines 
as  compared  with  engines  of  the  four-cycle  type  is  due  entirely  to  the 
fact  that  the  burned  gases  have  not  sufficient  time  in  which  to  escape 
from  the  combustion  space,  nor  the  fresh  charge  time  to  enter.  The 
fresh  charge  that  does  enter  is  incomplete  and  contaminated  by  the 
portion  of  the  burned  gases  that  have  not  been  able  to  escape.  This 
results  in  the  "choking  up"  of  the  engine,  and  in  the  production  of 
lower  power  than  the  dimensions  and  weight  of  the  engine  warrant. 

Automobile  engineers  agree  that  the  four-cycle  engine  is  better 
for  automobile  work.  It  has  been  developed  to  a  greater  degree 
than  the  two-cycle  and  it  is  easier  to  keep  adjusted  and  in  good 
running  condition.  Though  the  two-cycle  engine  is  undoubtedly 
the  simplest  form,  it  is  liable  to  be  erratic  in  operation  and  it  is  some- 
times difficult  to  locate  the  trouble  definitely.  The  following  ad- 
vantages are  claimed  for  the  two-cycle  engine  over  the  four-cycle: 

(1)  absence  of  poppet  valves  with  their  springs,  push  rods,  cam 
shafts,  etc.;  (2)  fewer  parts;  (3)  better  turning  effect  with  the  same 
number  of  cylinders.    Offsetting  these,  the  four-cycle  engine  has  the 
following  advantages  over  the  two-cycle:    (1)  greater  fuel  economy, 

(2)  greater  flexibility.    These   advantages    far    over-balance    the 
advantages  of  the  two-cycle  over  the  four-cycle  engine  and  for  that 
reason  the  two-cycle  engine  is  very  rarely  used  for  automobile 
propulsion. 


CHAPTER  III 


TIMING 

As  explained  in  the  operation  of  the  four-cycle  engine,  the  inlet 
valve  is  opened  during  the  suction  stroke  and  the  exhaust  valve  is 
opened  during  the  exhaust  stroke.  In  this  chapter  will  be  shown 
the  exact  time  at  which  the  valves  open  and  close  with  reference  to 
the  position  of  the  piston.  In  outlining  the  timing  of  the  valves, 
the  reason  for  each  operation  of  the  valve  will  be  explained. 

During  the  inlet  stroke,  the  inlet  valve  must  be  open  to  admit 
the  charge.  The  charge  is  forced  into  the  cylinder  due  to  the  pres- 
sure being  reduced  as  the  piston  moves  outward.  If  the  inlet  valve 
were  opened  at  top  dead  center,  the  gases  would  not  be  forced  into 
the  cylinder  until  the  piston  had  moved  out  sufficiently  to  cause  a 
decrease  in  pressure  and  the  velocity  of  the  incoming  gases  for  some 
time  would  be  slow.  In  order  to  prevent  this,  the  inlet  valve  remains 
closed  for  a  certain  number  of  degrees  during  the  downward  move 
ment  of  the  piston.  This  causes  a  sufficient  decrease  in  pressure  to 
allow  the  gases  to  be  forced  in  with  a  certain  amount  of  initial  velocity. 
Most  manufacturers  have  adopted  this  practice  as  the  cylinder  will 
be  filled  more  rapidly. 

The  rapid  decrease  in  pressure  in  the  cylinder  due  to  the  outward 
movement  of  the  piston  causes  the  gases  to  rush  in  and  fill  up  the 
space  back  of  the  piston.  If  the  piston  moves  slowly,  the  mixture 
will  be  able  to  enter  fast  enough  to  keep  the  pressure  in  the  com- 
bustion space  equal  to  that  outside.  At  the  high  speed  at  which  a 
gasoline  engine  runs,  the  piston  will  reach  the  end  of  its  stroke  before 
a  complete  charge  has  had  time  to  enter  through  the  small  inlet 
valve  opening.  Therefore  the  pressure  in  the  combustion  space  will 
still  be  below  that  of  the  atmosphere.  If  the  inlet  valve  closed  at 
this  point  so  that  no  more  mixture  could  enter,  the  combustion  of 
the  partial  charge  would  result  in  a  lower  pressure  than  would  be 
possible  with  a  full  charge.  The  inlet  valve  should  therefore  remain 
open  until  the  piston  reaches  a  point  in  its  next  inward  stroke  at 
which  the  pressure  in  the  cylinder  equals  that  outside.  The  piston 
moving  inward  diminishes  the  space  in  the  cylinder  and  compresses 
the  gas  ahead  of  it.  When  under  compression,  the  gas  is  ready  to 
be  ignited  and  burned. 

The  combustion  of  the  inflammable  mixture  produces  a  certain 
amount  of  heat.  The  more  rapid  and  complete  this  combustion,  the 


14 


TIMING  15 

greater  and  more  sudden  will  be  the  rise  in  pressure.  The  pressure 
will  be  greater  when  the  mixture  is  contained  in  a  small  space  than 
when  in  a  large  space.  As  the  combustion  space  is  smallest  when 
the  piston  is  at  its  inmost  point,  the  greatest  pressure  will  be  obtained 
if  combustion  is  completed  at  this  pointc  If  the  combustion  of  the 
mixture  were  instantaneous,  it  would  be  ignited  at  this  point.  But 
even  though  very  rapid,  it  burns  slowly  enough  to  make  necessary 
the  ignition  of  the  mixture  before  the  end  of  the  stroke.  The  com- 
bustion will  then  be  complete  as  the  piston  comes  into  position  to 
move  outward.  The  instant  at  which  the  mixture  must  be  ignited 
in  order  to  produce  this  result  depends  on  the  speed  of  the  piston. 
The  interval  between  the  ignition  of  a  good  mixture  and  its  complete 
combustion  does  not  vary  to  any  great  extent.  When  the  piston  is 
moving  slowly,  the  mixture  may  be  ignited  toward  the  end  of  the 
compression  stroke,  for  there  will  be  sufficient  time  for  complete 
combustion  by  the  time  the  stroke  is  ended.  When  moving  at  high 
speed,  ignition  must  occur  much  earlier  in  the  stroke,  as  otherwise 
the  piston  will  have  completed  the  compression  stroke  and  begun  to 
move  outward  on  the  power  stroke  before  the  mixture  is  entirely 
burned.  The  instant  at  which  ignition  occurs  also  depends  on  the 
mixture  that  is  used,  since  this  makes  a  difference  in  the  rapidity  with 
which  it  burns.  The  better  the  quality  of  the  mixture,  the  faster 
and  more  completely  it  will  burn  and  ignition  may  occur  later  in  the 
stroke  than  would  be  possible  with  a  mixture  of  poorer  quality.  The 
instant  at  which  ignition  occurs  may  be  controlled  by  causing  the 
spark  to  take  place  earlier  or  later,  this  being  controlled  by  the 
driver. 

When  ignition  occurs  early  in  the  compression  stroke,  the  spark 
is  said  to  be  advanced.  A  retarded  spark  takes  place  when  the  com- 
pression stroke  is  more  nearly  complete. 

If  the  spark  is  advanced  too  much,  combustion  will  be  complete 
before  the  piston  has  reached  the  end  of  the  compression  stroke.  It 
will  then  be  necessary  to  force  the  piston  inward  against  the  resultant 
pressure  by  the  momentum  of  the  flywheel,  in  order  that  it  may  get 
into  position  to  move  outward  on  the  power  stroke.  In  such  a  case, 
the  momentum  may  not  be  sufficient  to  overcome  the  pressure  and 
the  piston  will  be  brought  to  a  stop. 

A  retarded  spark  often  results  in  the  complete  combustion  of  the 
mixture  after  the  piston  has  begun  to  move  outward  on  the  power 
stroke.  The  pressure  will  then  be  reduced  because  combustion  takes 
place  in  a  larger  space,  the  piston  consequently  being  moved  with 
less  force.  If  the  spark  is  still  further  retarded,  the  combustion  will 
not  be  completed  by  the  time  exhaust  begins.  The  heat  from  only 


16  MOTOR  VEHICLES  AND  THEIR  ENGINES 

a  portion  of  the  mixture  will  then  be  utilized  because  the  gases  will 
still  be  burning  as  they  are  forced  out  of  the  cylinder. 

The  position  at  which  the  spark  occurs  should  be  governed  by 
the  speed  of  the  engine.  The  low  pressure  that  results  from  a 
retarded  spark  moves  the  piston  at  low  speed,  while  the  high  pressure 
from  an  advanced  spark  drives  the  piston  outward  with  more  force 
and  greater  velocity. 

While  high  compression  of  the  charge  improves  its  quality  and 
results  in  combustion  being  more  rapid  and  complete,  it  has  limits, 
and  if  carried  too  far  the  heat  generated  by  the  compression  will  be 
sufficient  to  ignite  the  mixture.  This  would  have  a  bad  effect  on  the 
operation  of  the  engine,  for  the  pressure  would  then  be  produced  at 
the  wrong  point  in  the  stroke,  retarding  instead  of  assisting  the 
revolution  of  the  crank  shaft. 

As  the  piston  is  forced  outward  by  the  expanding  gases,  it  has 
been  found  necessary  to  open  the  exhaust  valve  before  the  piston 
reaches  the  end  of  its  stroke.  Even  if  this  wastes  some  of  the  force 
of  the  expansion,  it  is  amply  compensated  for  by  the  freedom  afforded 
the  piston  in  commencing  the  exhaust  stroke.  By  opening  the 
exhaust  valve,  before  the  piston  reaches  the  end  of  its  power  stroke, 
the  gases  will  have  an  outlet  for  expansion  and  begin  to  rush  out  of 
their  own  accord.  This  removes  the  greater  part  of  the  burned 
gases,  reducing  the  amount  of  work  to  be  done  by  the  piston  on  its 
return  stroke.  Obviously  it  would  be  wrong  to  keep  the  exhaust 
valve  closed  up  to  the  very  moment  when  the  piston  is  about  to 
move  inward.  When  commencing  the  exhaust  stroke,  the  piston 
would  be  confronted  for  an  instant  with  the  force  which  had  just 
driven  it  down  and  until  the  valve  was  wide  open  there  would  be  a 
considerable  loss  of  power.  If  the  exhaust  valve  opens  too  early, 
there  will  be  a  waste  of  power  because  the  gases  exhausted  could 
still  have  exerted  a  pressure  on  the  piston.  During  the  next  inward 
stroke,  the  remaining  gases  are  forced  out  of  the  open  exhaust  valve 
as  the  pressure  in  the  cylinder  exceeds  that  in  the  exhaust  manifold. 
This  causes  a  slight  compression  of  the  gases  ahead  of  the  piston  and 
when  it  reaches  its  inmost  position  there  will  be  a  certain  amount  of 
compressed  exhaust  gases  in  the  clearance  space. 

If  the  exhaust  valve  is  closed  at  this  point,  a  portion  of  these 
gases  will  still  be  retained  in  the  cylinder.  The  best  results  are 
obtained,  not  by  closing  the  exhaust  valve  at  the  end  of  the  exhaust 
stroke,  but  at  a  short  time  after  the  piston  has  begun  to  move  out- 
ward. It  would  appear  that  this  would  result  in  drawing  the  exhaust 
gases  back  into  the  cylinder.  However,  this  is  governed  by  two 
conditions:  first,  the  gases  under  compression  exceed  the  pressure 


TIMING 


17 


H^,,,: 


"""X 


Fig.  8— Rock  of  Piston 

in  the  exhaust  manifold  and  will  continue  to  flow  out  due  to  this 
difference  in  pressure;  second,  the  piston  while  at  the  top  of  the 
stroke  moves  but  very  little  for  10  to  15  degrees  movement  of  the 
crank  shaft.  This  does  not  materially  increase  the  combustion 
space. 

It  will  be  seen  that  this  is  true  by  referring  to  Fig.  8.  When  the 
crank  arms  are  in  a  position  as  shown  at  A,  for  a  certain  number 
of  degrees  movement  of  the  crank  shaft,  the  piston  will  move  upward 
for  a  certain  distance.  When  the  crank  arms  are  at  point  B,  for 
the  same  number  of  degrees  movement  of  the  crank  shaft,  the  dis- 
tance moved  by  the  piston  will  be  less.  When  the  crank  arms  are 
at  point  C,  for  the  same  number  of  degrees  there  is  very  little 
upward  movement  of  the  piston.  Between  certain  points  it  can  be 
seen  that  there  is  practically  no  motion  of  the  piston  which  is  called 
the  "rock  of  the  piston."  This  is  usually  the  amount  that  the 
exhaust  valve  is  left  open  after  top  dead  center. 

Diagrams  showing  the  exact  timing  of  the  valves  on  several  en- 
gines are  shown  in  Figs.  9  to  12,  inclusive.  From  these  diagrams, 
comparisons  may  be  made  as  to  the  time  the  valves  open  and  close 
in  different  designs  of  engine. 

Referring  to  the  valve  timing  diagrams,  it  will  be  seen  that  the 
point  at  which  the  inlet  valve  opens  is  approximately  the  same  on 
these  four  standard  engines  which  are  designed  to  run  at  different 
speeds  and  for  different  kinds  of  work.  On  practically  all  engines, 
the  inlet  valves  open  approximately  11  degrees  after  top  dead  center. 

The  point  at  which  an  inlet  valve  closes  depends  upon  a  great 
many  conditions,  the  principal  ones  being  the  maximum  speed  for 
which  the  engine  is  designed  and  the  size  and  location  of  the  valves. 
The  average  point  for  closing  the  inlet  valve  is  about  35  degrees 


18 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


B.  AC. 


Fig.  9 

HOLT 

1.  Inlet    valve    opens   10°  after  T.  D.  C. 

2.  Inlet    valve    closes   10°  after  B.  D.  C. 

3.  Exhaust  valve  opens  30°  before  B.  D.  C. 

4.  Exhaust  valve  closes    5°  after  T.  D.  C. 


Fig.  10 


DODGE 
10°  after  T.  D.  C. 
35°  after  B.  D.  C. 
45°  before  B.  D.  C. 
8°  after  T.  D.  C. 


T.0.C. 


•A  AC. 


Fig.  11 

WHITE 

1.  Inlet    valve    opens    10°  after  T.  D.  C. 

2.  Inlet    valve    closes    40°  after  B.  D.  C. 

3.  Exhaust  valve  opens  40°  before  B.  D.  C. 

4.  Exhaust  valve  closes    8°  after  T.  D.  C. 


Fig.  12 

F.  W.  D. 

15°  after  T.  D.  C. 
45°  after  B.  D.  C. 
45°  before  B.  D.  C. 
10°  after  T.  D.  C 


The  above  diagrams  each  represent  the  two  revolutions  of  the 
crank  shaft  necessary  to  complete  one  cycle. 


TIMING 


19 


after  bottom  dead  center.  The  valve  closes  later  on  high  speed 
engines  and  earlier  on  slow  speed  engines. 

The  point  at  which  the  exhaust  valve  opens  also  varies  consider- 
ably and  depends  upon  the  same  conditions  as  the  closing  of  the 
inlet  valve.  The  average  point  for  opening  the  exhaust  valve  is 
45  degrees  before  bottom  dead  center.  It  will  be  earlier  on  high 
speed  engines  and  later  on  slow  speed  engines. 

The  exhaust  valves  of  the  engines  represented  in  the  timing 
diagrams  all  close  at  approximately  the  same  point.  This  is  true  of 
practically  all  types  of  engines,  the  average  point  for  closing  the 
exhaust  valve  being  6  degrees  after  top  dead  center.  This  point  is 
limited  by  the  duration  of  the  rock  of  the  piston  and  hence  cannot 
vary  greatly. 

Fig.  13  shows  a  valve  timing  diagram  made  up  from  the  average 
points  at  which  the  valves  open  and  close  on  engines  of  American 
design.  It  is  a  good  guide  for  the  approximate  timing  of  the  valves 
of  an  engine  in  case  the  exact  timing  is  not  known.  However,  it 
must  never  be  used  for  accurately  setting  the  valves  on  any  engine. 


1.  Inlet    opens     11°  after  T.  D.  C. 

2.  Inlet    closes     35°  after  B.  D.  C. 

3.  Exhaust  opens  45°  before  B.  D.  C. 

4.  Exhaust  closes  6°  after  T.  D.  C. 
Suction  204° 
Compression   145° 

Power  135° 

Exhaust          231° 


ZAC. 


Fig.  13 — Valve  Timing  of  Average 
Engine 

If  for  any  reason  it  is  necessary  to  disassemble  the  engine,  the 
timing  gears  should  be  punched  so  as  to  indicate  where  they  should 
mesh  when  they  are  again  assembled  in  order  to  have  the  proper 
timing  of  the  valves.  If  an  engine  is  received  with  the  flywheel 
unmarked,  the  first  duty  for  the  man  in  charge  of  the  apparatus  is  to 
see  that  the  flywheel  is  marked  correctly  in  order  to  have  some  accur- 
ate method  of  checking  up  valve-timing  and  valve-clearance  at  all 
times.  Marking  the  flywheel  is  a  very  simple  matter  and  will  elimi- 


20  MOTOR  VEHICLES  AND  THEIR  ENGINES 

nate  endless  trouble  whenever  any  repairs  are  made  to  the  engine 
where  disassembling  is  necessary. 

In  case  a  crank  shaft  is  offset  from  the  center  line  of  the  cylinders, 
the  exhaust  valves  will  usually  close  at  top  dead  center,  as  the  rock 
of  the  piston  at  this  point  has  been  eliminated.  The  reason  for  such 
design  is  that  when  the  maximum  expansion  occurs  at  top  dead 
center,  there  will  not  be  a  direct  downward  thrust  on  the  crank  shaft 
and  connecting  rod  bearings. 


CHAPTER  IV 


ENGINE  BALANCE  AND  FIRING  ORDER 

The  term  engine  balance  includes  both  power  balance  and  me- 
chanical balance  of  the  engine.  An  engine  has  power  balance  when 
the  power  impulses  occur  at  regular  intervals  in  relation  to  the  revolu- 
tion of  the  crank  shaft.  In  many  types  of  engines  the  power  impulses 
do  not  occur  regularly  and  there  is  an  uneven  distribution  of  power. 
The  power  balance  of  various  types  of  engines  will  be  discussed  in  this 
chapter.  An  engine  has  mechanical  balance  when  the  moving  parts 
are  so  arranged  as  to  counterbalance  in  their  operation  and  thereby 
reduce  vibration. 

The  difficulty  in  constructing  reciprocating  engines  is  that  the 
weight  of  the  pistons  and  connecting  rods  in  moving  first  one  way 
and  then  the  other,  produces  great  vibration.  The  crank  shaft  in 
bringing  these  parts  to  a  stop  at  the  end  of  each  stroke,  is  subjected 
to  violent  shocks  which  in  time  wear  it  loose  in  its  bearings.  With 
internal  combustion  engines,  this  vibration  and  the  shock  on  the  crank 
shaft  are  greatly  increased  by  the  intensity  with  which  the  pressure 
is  exerted  on  the  piston. 

In  a  well-designed  engine,  the  manufacturer  is  very  careful  to  see 
that  every  piston  and  connecting  rod  is  of  identically  the  same  weight 
and  that  the  fly  wheel  and  crank  shaft  have  a  perfect  running  balance. 
By  this  practice  a  considerable  amount  of  the  vibration  will  be 
eliminated. 

In  a  one-cylinder  engine  (Fig.  14)  there  is  but  one  power  impulse 
during  two  revolutions  of  the  crank  shaft.  Therefore  there  will  be 
an  uneven  distribution  of  power.  Since  there  is  but  one  piston  and 
connecting  rod  which  reciprocate  with  no  working  parts  to  counter- 


Fig.  14 — One-Cylinder  Power  Balance  Chart 
21 


22 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


balance  their  weight,  the  engine  will  not  have  mechanical  balance. 
The  engine  can,  however,  be  balanced  to  some  extent  by  the  use  of 
counterweights  attached  to  the  crank  shaft  and  also  by  the  use  of  a 
fly  wheel  so  heavy  that  its  momentum  produces  a  comparatively 
steady  movement.  Fluctuations  in  the  speed  of  the  engine  will 
cause  vibration  even  under  the  most  favorable  conditions  which 
makes  the  one-cylinder  engine  undesirable  for  motor  vehicles. 

In  two-cylinder  engines,  the  vibration  may  be  reduced  by  ar- 
ranging the  parts  so  as  to  have  the  pistons  move  in  opposite  direc- 
tions, thus  counterbalancing  each  other.  This  is  the  plan  of  con- 
struction used  in  the  horizontal  double  opposed  engine  (Fig.  15). 
The  cylinders  are  horizontal  and  arranged  on  opposite  sides  of  a 
two-throw  180°  crank  shaft.  That  is,  there  are  two  pairs  of  crank 


Fig.  15 — Two-Cylinder  Opposed  Power  Balance  Chart 

arms  projecting  from  opposite  sides  of  the  shaft  so  that  they  are  one- 
half  a  revolution  apart.  An  engine  of  this  construction  has  good 
mechanical  balance. 

To  fully  understand  the  power  balance  as  shown  in  the  table, 
the  order  in  which  the  strokes  of  a  four-cycle  engine  occur  must  be 
recalled.  The  two  outward  strokes  are  suction  and  power  and  the  two 
inward  strokes  compression  and  exhaust.  If  piston  number  one  is 
moving  outward  on  power,  then  piston  number  two  must  be  moving 
out  on  suction,  and  for  the  next  half  revolution  or  inward  strokes  of 
the  pistons,  number  one  piston  will  be  exhausting  the  gases  while 
number  two  piston  is  compressing  the  charge.  During  the  second 
revolution  of  the  crank  shaft,  number  two  piston  will  move  outward  on 
power  while  number  one  moves  outward  on  suction  and  during  the  in- 
ward strokes  of  the  pistons,  number  two  is  exhausting  the  burned  gases 
while  number  one  is  compressing  a  fresh  charge.  In  this  way,  one 
power  impulse  is  obtained  during  each  revolution  of  the  crank  shaft. 
This  engine  has  both  power  balance  and  mechanical  balance. 

Two-cylinder  engines  are  also  built  with  vertical  cylinders  and 
are  classed  according  to  the  construction  of  their  crank  shafts.  One 


ENGINE  BALANCE  AND  FIRING  ORDER 


23 


has  a  180°  crank  shaft  which  is  identical  with  that  used  in  the  two- 
cylinder  opposed  engine.  The  other  has  a  360°  crank  shaft,  which 
has  both  pairs  of  crank  arms  projecting  from  the  same  side  of  the 
shaft,  so  that  the  crank  pins  are  in  line. 


Fig.  16— Two-Cylinder  180°  Crank  Shaft  Power  Balance  Chart 

In  the  two-cylinder  180°  crank  shaft  construction  (Fig.  16) 
number  one  piston  is  moving  outward  as  number  two  piston  is  moving 
inward;  in  other  words,  the  pistons  move  in  opposite  directions. 
An  engine  of  this  construction  has  good  mechanical  balance. 

If  piston  number  one  is  moving  outward  on  power,  piston  number 
two  can  be  moving  inward  either  on  compression  or  exhaust.  In 
table  one,  the  power  balance  is  worked  out  with  piston  number  two 
moving  inward  on  compression  and  it  is  clearly  shown  that  both 
power  impulses  occur  during  the  first  revolution  while  there  are  no 
power  impulses  during  the  second  revolution.  In  table  two  the 
power  balance  is  worked  out  with  piston  number  two  moving  inward 
on  exhaust.  This  arrangement  gives  a  power  impulse  at  the  begin- 
ning of  the  first  revolution  and  at  the  end  of  the  second,  producing 
the  same  result  as  obtained  in  table  one.  In  either  case  there  is  an 
irregular  production  of  power  which  sets  up  strains  in  the  engine 
which  causes  it  to  run  unevenly.  This  results  in  poor  power  balance. 

In  the  two-cylinder  vertical  engine  with  a  360°  crank  shaft,  the 
pistons  move  up  and  down  together  causing  bad  mechanical  balance 
(Fig.  17). 

With  this  arrangement  the  application  of  power  may  be  evenly 
distributed  for  as  number  one  piston  moves  outward  on  power, 
piston  number  two  could  move  outward  on  either  power  or  suction. 
There  would  be  no  advantage  in  having  both  cylinders  firing  at  the 
same  time,  hence  number  two  piston  moves  outwards  on  suction. 
As  shown  in  the  table,  during  the  first  revolution,  number  one  piston 
is  on  power  and  exhaust  while  number  two  piston  is  on  suction  and 
compression.  During  the  second  revolution  number  one  piston  is 


24 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


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Fig.  17 — Two-Cylinder  360°  Crank  Shaft  Power  Balance  Chart 

on  suction  and  compression  while  number  two  piston  is  on  power  and 
exhaust.  With  this,  arrangement  there  is  a  power  impulse  at  the 
beginning  of  each  revolution  of  the  crank  shaft  and  the  engine  has 
power  balance. 

The  defects  of  two-cylinder  vertical  engines  with  either  design 
of  crank  shaft  outweigh  any  possible  advantage  of  that  construction. 
The  horizontal  double  opposed  type  with  evenly  occurring  power 
impulses,  mechanical  balance,  and  simplicity  of  construction  is 
frequently  used  on  small  trucks. 

With  a  four-cylinder  engine  a  180°  crank  shaft  is  always  used 
(Fig.  18).  The  crank  arms  for  numbers  one  and  four  cylinders  pro- 
ject in  the  same  direction  and  the  crank  arms  for  numbers  two  and 
three  cylinders  project  from  the  opposite  side  of  the  crank  shaft. 
This  arrangement  is  used  in  preference  to  having  the  cranks  projecting 
alternately,  that  is,  one  and  three  to  one  side  and  two  and  four  to  the 
other,  because  greater  vibration  and  strain  on  the  crank  shaft  would 
result  with  this  construction.  The  form  of  crank  shaft  commonly 
used  does  not  permit  a  firing  order  of  1-2-3-4,  but  gives  firing  orders 
in  which  numbers  one  and  four  must  fire  alternately.  The  succession 
in  which  power  strokes  occur  is  called  the  firing  order. 

In  the  four-cylinder  engine  numbers  one  and  four  pistons  are 
always  moving  in  the  opposite  direction  from  numbers  two  and  three. 
If  equal  in  weight  they  will  balance  each  other  and  an  engine  of  this 
type  is  said  to  have  good  mechanical  balance. 

As  number  one  piston  is  moving  outward  on  power,  number  four 
must  move  outward  on  suction;  number  two  piston  can  be  moving 
inward  on  exhaust  or  compression  and  number  three  will  be  moving 
inward  on  compression  or  exhaust.  Table  one  shows  the  power 
balance  with  number  two  piston  on  exhaust  and  number  three  on 
compression.  Table  two  shows  the  power  balance  resulting  from 
number  two  piston  moving  inward  on  compression  and  number. 


ENGINE  BALANCE  AND  FIRING  ORDER 


25 


three  on  exhaust.    With  either  arrangement  the  power  impulses 
are  evenly  distributed,  that  is,  they  are  180°  apart. 


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Fig.  18 — Four-Cylinder  Power  Balance  Chart 

Each  arrangement  gives  a  different  firing  order.  With  the 
arrangement  shown  in  table  one  the  firing  orders  is  1-3-4-2.  With 
the  arrangement  shown  in  table  two  the  firing  order  is  1-2-4-3. 
Following  are  the  firing  orders  of  four-cylinder  engines  in  several 
motor  vehicles.  It  will  be  noted  that  the  firing  order  1-3-4-2  is 
the  most  common. 

Four-Wheel  Artillery  Tractor 1-3-4-2 

F.  W.  D.  1-3-4-2 


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Ford  . 


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1-2-4-3 
1-2-4-3 
1-2-4-3 


Three-cylinder  engines  are  built  with  120°  crank  shafts,  that  is, 
the  crank  arms  are  J^  of  a  revolution  apart  instead  of  J^  revolution 


26 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


as  in  the  180°  crank  shafts.  With  this  arrangement  as  shown  in 
Fig.  19,  number  one  piston  moves  outward  on  power,  number  two 
piston  moves  inward  finishing  its  exhaust  stroke  and  starts  outward 


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on  suction,  number  three  piston  moves  outward  finishing  its  suction 
stroke  and  starts  inward  on  compression.  As  number  one  piston 
moves  inward  on  exhaust,  number  two  piston  finishes  its  suction 
stroke  and  starts  inward  OR  compression,  number  three  piston  finishes 
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finishes  its  power  stroke  and  starts  inward  on  exhaust,  number  three 
piston  finishes  the  exhaust  stroke  and  starts  outward  on  suction. 
From  the  foregoing  it  can  readily  be  seen  that  the  power  impulses 
will  occur  every  240°  movement  of  the  crank  shaft.  An  engine  of 
this  type  has  power  balance. 

Six-cylinder  engines  have  crank  shafts  of  a  similar  construction 
to  the  three-cylinder;  having  numbers  one  and  six,  two  and  five,  and 
three  and  four  pistons  operating  together.  With  this  construction 
there  will  be  six  power  impulses  during  two  revolutions  which  gives 
very  good  engine  balance. 

In  Fig.  20  it  will  be  seen  that  as  numbers  one  and  six  pistons  are 
starting  outward,  numbers  two  and  five  are  completing  their  outward 
strokes,  and  numbers  three  and  four  are  on  their  inward  strokes. 
With  this  arrangement  it  is  possible  to  obtain  four  different  combina- 
tions as  shown  in  tables  one,  two,  three,  and  four.  It  is  also  possible 
to  have  numbers  three  and  four  pistons  finishing  their  outward  strokes 
as  numbers  one  and  six  start  outward  and  two  and  five  complete  their 
inward  strokes.  Combinations  as  shown  in  tables  five,  six,  seven, 
and  eight  will  result.  With  any  of  these  combinations  it  can  be 


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27 


28  MOTOR  VEHICLES  AND  THEIR  ENGINES 

readily  seen  that  the  power  impulses  are  evenly  distributed  and  are 
120°  apart,  the  only  difference  being  the  order  in  which  the  cylinders 
fire. 

Table  1.— Firing  Order  1-3-5-6-4-2 
Table  2.— Firing  Order  1-4-5-6-3-^- 
Table  3.— Firing  Order  1-3-2-6-4-5 
wTable  4.— Firing  Order  1-4-2-6-3-5 
Table  5.— Firing  Order  1-2-4-6-5-3 
Table  6.— Firing  Order  1-5-4-6-2-3 
Table  7.— Firing  Order  1-2-3-6-5-4- 
V  Table  8.— Firing  Order  1-5-3-6-2-4 

Although  there  are  eight  possible  firing  orders  there  are  only 
four  which  are  commonly  used.  The  following  are  seldom  used: 
l_2_3_6-5-4,  1-5-4-6-2-3,  1-3-2-6-4-5,  and  1-4-5-6-3-2.  With 
any  of  these  firing  orders  the  three-cylinder  at  one  end  of  the  crank 
shaft  fire  and  then  the  three  at  the  other  end  fire,  setting  up  vibration 
due  to  the  concentration  of  the  power  impulses.  For  this  reason, 
six-cylinder  engines  are  commonly  built  to  fire  so  that  the  impulses 
are.  evenly  distributed  along  the  crank  shaft. 

Eight-cylinder  engines  for  motor  vehicles  are  usually  constructed 
by  arranging  two  four-cylinder  engines  to  operate  from  a  single  four- 
throw  180°  crank  shaft  of  the  same  form  used  in  the  four-cylinder 
engine.  The  cylinders  are  set  so  that  their  center  lines  form  an  angle 
90°  and  for  this  reason  such  engines  are  called  "V  Type."  The  con- 
necting rods  of  the  cylinders  on  the  right  operate  on  the  same  crank 
pins  as  the  corresponding  connecting  rods  for  the  cylinders  on  the 
left.  It  must  be  borne  in  mind  that  these  connecting  rods  operate 
independently  of  each  other.  Therefore  the  operations  of  the 
cylinders  on  the  right  are  always  90°  different  from  the  cylinders  on 
the  left,  that  is,  when  number  one  piston  on  the  right  is  at  top  dead 
center,  number  one  piston  on  the  left  will  have  completed  one-half 
its  stroke  (Fig.  21). 

The  table  showing  the  power  balance  is  based  on  the  arrangement 
used  in  the  Cadillac  "8."  As  number  one  piston  on  the  left  is 
moving  outward  on  power,  number  four  piston  on  the  left  is  mov- 
ing outward  on  suction,  number  two  piston  on  the  left  moving  in- 
ward on  exhaust,  and  number  three  piston  on  the  left  moving  inward 
on  compression.  The  movements  on  the  right  hand  side  will  be  half 
completed,  therefore,  number  one  piston  will  be  completing  suction, 
number  four  piston  will  be  completing  power,  number  two  piston 
will  be  completing  compression,  and  number  three  piston  will  be 
completing  exhaust.  Working  out  the  operations  for  each  90°  move- 
ment of  the  crank  shaft  will  give  the  results  shown  in  the  table. 


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Fig.  21 — Eight-Cylinder  Power  Balance  Chart 

29 


30  MOTOR  VEHICLES  AND  THEIR  ENGINES 

There  is  a  power  impulse  for  every  90°  movement  of  the  crank  shaft, 
giving  a  firing  order  as  follows :  lL-2R-3L-lR-4Lr-3R-2L-4R.  The 
power  impulses  are  regular  and  very  frequent  in  an  engine  of  this 
type  insuring  very  good  engine  balance. 

The  twelve-cylinder  engine  is  also  a  "V  Type"  and  consists  of 
two  sets  of  six  cylinders  arranged  similarly  to  the  "V  Type"  eight- 
cylinder  engine  except  that  the  angle  between  the  center  lines  of  the 
cylinders  is  60°.  A  regular  six-throw  120°  crank  shaft  is  used,  two 
connecting  rods  being  attached  to  each  crank  pin  (Fig.  22).  The 
table  shown  is  based  on  the  arrangement  used  in  the  Packard  Twin 
Six;  starting  with  number  one  piston  on  the  right  at  top  dead  center 
and  moving  the  engine  60°  or  one-third  of  a  complete  stroke  and 
showing  the  changes  that  take  place.  This  table  shows  that  a  fresh 
power  impulse  is  given  the  crank  shaft  for  each  60°  movement  which 
gives  unusually  good  engine  balance.  The  firing  order  of  this  engiue 
is  lR-6L-4R-3L-2R-5L-6R-lLr-3R-4Lr-5R-2L. 

There  are  many  possible  firing  orders  for  eight  and  twelve- 
cylinder  "V  Type"  engines  other  than  the  ones  given.  The  firing 
order  depends  upon  the  arrangement  of  the  cams  on  the  cam  shaft 
and  any  combination  will  give  equally  good  power  balance. 

The  one-cylinder  engine  having  but  one  power  impulse  for  two 
revolutions  of  the  crank  shaft  does  not  run  smoothly  or  quietly  due 
to  the  size  of  the  cylinder  and  time  between  impulses.  This  fact  led 
to  the  adoption  of  the  two,  four,  and  six-cylinder  engines  and  quite 
recently,  the  eight  and  twelve-cylinder  engines  have  come  into  use. 
As  the  number  of  cylinders  is  increased,  the  power  impulses  increase 
in  frequency.  The  average  power  is  greater  and  above^four  cylinders 
there  is  no  period  during  which  some  cylinder  is  not  delivering  power. 
This  means  that  in  a  six,  eight,  or  twelve-cylinder  engine  there  is 
no  time  at  which  the  fly  wheel  must  supply  all  the  power  required 
to  maintain  the  engine  speed. 

The  multi-cylinder  engine,  therefore,  furnishes  a  practically  con- 
tinuous flow  of  power  with  little  vibration.  The  increase  in  the 
number  of  cylinders  permits  reduction  in  the  size  of  each  cylinder  and 
this  combined  with  the  steady  operation  of  the  engine  makes  the 
modern  automobile  engine  a  very  quiet,  smooth-running,  power  unit. 

As  shown  in  valve  timing,  the  average  length  of  the  power  impulse 
is  145°  and  from  Fig.  23  it  can  be  seen  that  as  the  number  of  cylinders 
is  increased  the  power  impulses  extend  over  a  greater  range.  For 
engines  having  more  than  four  cylinders  the  power  impulses  are  con- 
tinuous and  overlap,  the  length  of  overlap  increasing  with  the 
number  of  cylinders. 


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Fig.  22 — Twelve-Cylinder  Power  Balance  Chart 

31 


s0f, 


Fig.  23— Power  Overlap  Charts 

32 


ENGINE  BALANCE  AND  FIRING  ORDER  33 

Engines  of  more  than  four  cylinders  will  have  several  possible 
firing  orders.  The  exact  firing  order  of  the  engine  will  depend  upon 
the  arrangement  of  the  cams  on  the  cam  shaft.  Therefore,  the  firing 
order  can  be  determined  by  checking  a  certain  operation  of  the  valves 
such  as  the  opening  of  the  inlet  or  the  opening  of  the  exhaust,  or  by 
checking  the  compression.  The  firing  order  thus  obtained  will  cor- 
respond to  that  of  the  power  balance  chart  worked  out  for  any 
particular  engine.  For  example,  take  the  power  balance  chart  of  a 
four-cylinder  engine,  as  shown  in  Fig.  18.  If  the  order  in  which  the 
suction  strokes,  the  exhaust  strokes,  or  the  compression  strokes 
occur  is  taken  the  same  firing  order  results. 


CHAPTER  V 


COOLING  SYSTEMS 

As  previously  shown  the  internal  combustion  engine  is  a  machine 
for  transforming  heat  into  mechanical  energy.  As  the  heat  increases 
a  greater  expansion  of  the  gases  results  and  more  power  is  developed. 
However,  there  are  certain  limitations  to  the  degree  of  heat  that  can 
be  maintained  in  the  engine  and  if  the  temperature  were  allowed  to 
rise  above  a  certain  limit  the  degree  attained  would  cause  mechanical 
troubles.  The  intense  heat  would  cause  the  cylinder  to  be  scored, 
the  valves  to  warp,  and  the  lubricant  to  be  burned  up  causing  the 
piston  and  bearings  to  bind.  It  would  also  cause  the  incoming 
charge  to  become  expanded  and  thereby  cause  a  rarefied  mixture. 
In  addition  to  these  things  the  spark  plugs  would  crack  and  the 
temper  would  be  taken  out  of  the  valve  springs.  From  this  it  can 
readily  be  seen  that  some  method  of  cooling  the  engine  must  be 
adopted. 

As  shown  in  the  second  chapter  a  considerable  amount  of  heat  is 
lost  in  cooling  but  this  cannot  be  materially  reduced  for  the  tempera- 
ture of  combustion  far  exceeds  the  temperature  at  which  the  engine 
^^^^^^^^m  could  operate.  The  duty  of  the 
cooling  system  is  to  keep  the  en- 
gine from  attaining  a  tempera- 
ture which  would  stop  its  opera- 
tion and  is  not  to  keep  the 
engine  cool,  for  in  so  doing  it 
would  increase  the  cooling  losses 
and  lower  the  efficiency.  It  is 
a  misinterpreted  idea  in  many 
cases  that  the  cooling  system  is 
to  keep  the  engine  very  cool. 
It  has  been  found  in  testing  en- 
gines that  they  operate  best 
when  the  water,  leaving  the 
water  jacket,  is  over  160°  but 
well  under  the  boiling  point. 
There  are  two  general  systems 
of  engine  cooling  in  common  use.  First,  by  air  which  cools  the 
engine  by  direct  radiation.  Second,  by  water  which  cools  the 
engine  and  is  subsequently  cooled  by  air. 

34 


Fig.  24 — Air-Cooled  Cylinder 


COOLING  SYSTEMS  35 

There  are  certain  things  which  must  be  taken  into  consideration 
when  cooling  an  engine  by  air.  First,  the  cooling  depends  upon  the 
amount  of  surface  presented  to  the  air.  Therefore  in  motor  cycles 
the  effective  outer  surfaces  of  the  cylinders  are  increased  by  the 
addition  of  fins  or  flanges  cast  on  them  and  presenting  a  greater 
surface  for  cooling  as  shown  in  Fig.  24.  Second,  the  cooling  depends 
upon  the  amount  of  air  passing  over  the  cooling  surface.  As  the 
amount  of  air  passing  over  this  surface  is  increased  the  cooling  will 
be  proportionately  increased.  On  motor-cycles  where  there  is  no 
fan  to  keep  the  air  in  circulation  it  is  essential  that  the  motor-cycle 
be  kept  in  motion  as  long  as  the  engine  is  running,  otherwise  over- 
heating of  the  engine  will  result.  Third,  the  cooling  depends  upon 
the  temperature  of  the  air  passing  over  the  cooling  surface.  This 
results  in  the  engine  being  kept  cooler  in  cold  weather  than  in  warm 
weather.  The  rear  cylinder  of  the  engine  will  not  be  cooled  the 
same  amount  as  the  front  cylinder.  This  is  because  the  air  becomes 
heated  after  passing  the  front  cylinder,  therefore,  it  cannot  have  an 
equal  cooling  effect  on  the  rear  cylinder. 

With  twin-cylinder  motor-cycles  difficulty  will  often  be  experi- 
enced with  the  rear  cylinder  due  to  this  unequal  cooling.  There  is 
more  probability  of  carbon  being  formed  in  this  cylinder  which  will 
lead  to  ignition  troubles  and  engine  troubles  in  general.  In  case  a 
miss  in  one  cylinder  is  noted  it  is  best  to  look  first  for  the  trouble  in 
the  rear  cylinder. 

Because  of  its  simplicity  and  light  weight  the  air-cooled  engine 
is  particularly  suitable  for  motor-cycle  engines.  The  small  size  of 
the  engine  together  with  its  exposed  cylinders  insures  proper  cooling 
and  makes  this  type  of  cooling  ideal  for  the  motor-cycle. 

When  water  is  employed  in  cooling  it  must  circulate  through 
jackets  around  the  combustion  chamber  and  be  kept  in  motion 
either  by  heat  or  forced  circulation.  The  water  is  heated  by  the 
cylinders  and  then  passes  to  the  radiator  where  it  is  cooled  by  air 
being  drawn  through  the  radiator  by  a  fan.  There  are  three  general 
systems  of  water  cooling  in  use:  the  Thermo  Syphon,  the  Force 
System,  and  Thermostatic  Controlled. 

The  THERMO-SYPHON  COOLING  SYSTEM,  shown  in  Fig. 
25,  is  a  typical  construction.  The  water  enters  the  cylinder  jacket 
at  "A"  and  upon  becoming  heated  by  the  combustion  within  the 
engine,  rises  and  enters  the  pipe  "B"  and  passes  to  the  radiator 
"C"  where  it  is  brought  into  contact  with  a  large  cooling  surface 
"D."  When  water  is  cooled  it  becomes  heavier  and  therefore  sinks 
to  the  bottom  of  the  cooling  system.  As  the  water  is  heated  in  the 
cylinder  jacket  and  rises  to  the  top  it  must  be  replaced  by  cool 


36 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


water  and  therefore  the  water  from  the  lower  pipe  "A"  enters  the 
water  jacket. 


Fig.  25 — Thermo-Syphon  Cooling  System 

It  can  readily  be  seen  that  this  circulation  is  proportional  to  the 
heat  and  as  the  heat  increases  the  circulation  becomes  faster.  This 
is  an  ideal  condition  for  keeping  the  engine  at  the  proper  tempera- 
ture. Since  there  could  be  no  circulation  when  the  engine  is  cold  the 
possibility  of  cold  water  continuously  passing  through  the  water 
jacket  is  eliminated,  a  condition  which  would  keep  the  engine  at  a 
temperature  less  than  should  be  maintained  for  proper  efficiency. 
As  the  circulation  depends  solely  upon  the  heat  it  is  not  positive  and 
a  slight  amount  of  foreign  matter  obstructing  the  passages  would 
interfere  with  the  circulation.  Another  objection  to  the  Thermo- 
Syphon  system  is  that  in  case  enough  water  evaporates,  the  water 
level  will  fall  below  the  pipe  entering  the  radiator,  the  circulation 
will  stop,  and  the  engine  overheat.  To  prevent  this  it  is  essential 
that  the  radiator  be  kept  completely  filled.  In  extremely  cold 
weather  freezing  of  the  lower  pipe  may  occur  after  the  car  has  been 
on  the  road  for  a  short  time.  This  is  due  to  the  circulation  being 
very  sluggish  in  cold  weather  and  the  last  point  reached  by  the  water 
warmed  in  the  cylinders  is  the  lower  pipe.  As  soon  as  freezing  takes 
place  circulation  stops  and  overheating  results.  The  water  in  the 
jackets  is  heated  and  rises  to  the  top  but  cannot  pass  down  through 


COOLING  SYSTEMS 


37 


the  radiator  to  be  cooled.  This  trouble  arises  from  not  running  the 
engine  sufficiently  to  warm  up  all  the  water  in  the  cooling  system 
before  starting  out. 


•  Radiator  Cap 

•  Filler  Neck 

•  Top  Tank 
•Splash  Plate 

•  Overflow  Tube 

•  Radiator  Tubes 
Rad  Inlet  Conn 

•Cyl.  Outlet  Hose 
Hose  Clip 


Cyl.nder  Head 
Cylinder  Casting 
Cylinder  Inlet  Connecuon 


Lower  Hose-. 

Lower  Hose  Clip 

Rad  Outlet  Conn        V  Quilei  Cona  Pipe 

Dram  Cock  Fan  Assb. 

Lower  Tank 


Fig.  26 — Ford  Cooling  System 

Fig.  26  shows  a  typical  Thermo-Syphon  system.  The  arrows 
indicate  the  course  of  the  water  through  the  water  passages.  This 
is  one  of  the  few  American  motor  cars  that  retains  the  Thermo- 
Syphon  cooling  system. 

THE  FORCE  COOLING  SYSTEM  shown  in  Fig.  27  is  a  typical 
construction.  In  this  system  water  leaves  the  cylinder  jackets 
through  the  pipe  from  the  cylinder  head  and  enters  the  radiator 
through  the  radiator  inlet  pipe.  The  water  passes  through  the  radia- 
tor where  it  is  cooled  by  the  air  drawn  through  the  radiator.  From 
the  radiator  the  water  passes  through  the  radiator  outlet  pipe  and 
through  the  pump  to  the  cylinder  jackets. 

While  the  engine  is  in  operation  the  pump,  being  geared  to  it, 
causes  the  water  to  circulate  so  that  slight  obstructions  will  not  clog 
up  the  system.  In  case  the  radiator  is  not  completely  filled  the 
pump  will  still  circulate  the  water  causing  it  to  overflow  from  the 
radiator  inlet  pipe.  The  only  part  of  the  system  in  which  there  will 
be  no  water  will  be  the  upper  section  of  the  radiator.  The  level  in 


38  MOTOR  VEHICLES  AND  THEIR  ENGINES 

the  radiator  will  depend  upon  the  quantity  of  water  in  the  system. 
If  there  is  too  little  water  the  level  will  be  so  low  that  the  efficiency 
of  the  radiator  in  cooling  the  water  will  be  reduced  to  such  an  extent 
that  overheating  will  often  result.  Since  the  water  is  always  in 
circulation  when  the  engine  is  running  there  is  little  possibility  of 
freezing. 


WAT'SR.  HOSE 


Fig.  2? — Dodge  Cooling  System, 

As  the  pump  is  positively  geared  to  the  engine  the  circulation  will 
be  proportional  to  its  speed  and  for  a  given  speed  the  amount  of 
cooling  will  vary  according  to  the  temperature  of  the  air.  On  a  cold 
day  as  much  water  is  passed  through  the  water  jackets  as  on  a  warm 
day,  but  the  temperature  of  the  water  is  considerably  lower  and  the 
engine  is  kept  too  cool  resulting  in  considerable  loss  of  efficiency. 
This  is  particularly  noticeable  when  starting  an  engine  in  cold 
weather  for  it  causes  misfiring  due  to  the  cold  water  being  circulated 
through  the  water  jackets.  To  prevent  excessive  cooling  of  the 
engine,  which  reduces  its  efficiency,  the  fan  may  be  disconnected 
thereby  reducing  the  cooling  power  of  the  radiator.  A  more  satis- 
factory method  is  to  cover  part  of  the  radiator's  cooling  surface.  The 
best  results  are  obtained  when  an  adjustable  device  or  shutter  is  used. 

Natural  circulation  is  of  practically  no  assistance  in  the  Force 
Cooling  System;  it  depends  entirely  upon  the  pump  for  circulation. 
This  permits  the  use  of  smaller  water  jackets  and  piping  and  as  it  is 
the  practice  to  construct  the  engine  as  light  as  possible,  these  are 
made  as  small  as  practicable.  In  case  any  difficulties  arise  which 
stop  the  operation  of  the  pump,  natural  circulation  cannot  be  de- 


COOLING  SYSTEMS 


pended  upon  to  sufficiently  cool  the  engine  as  it  does  in  the  Thermo- 
Syphon  System,  where  large  water  jackets  and  pipes  are  used. 

THE  THERMOSTATIC  CONTROLLED  COOLING  SYSTEM. 
— A  Thermostatic  device  is  introduced  in  this  system  in  order  to 
overcome  the  difficulties  which  arise  in  the  Forced  Cooling  System 
when  cooled  water  is  circulated  through  the  water  jackets.  The 
temperature  of  the  liquid  circulated  by  the  pump  is  under  Ther- 
mostatic control.  The  purpose  of  this  is  to  permit  water  circulating 
through  the  water  jackets  of  the  cylinders  and  carburetor  intake 
manifold  to  warm  up  to  the  temperature  at  which  the  engine  operates 
best,  very  soon  after  the  engine  is  started  and  to  prevent  the  tem- 
perature dropping  below  this  point  while  the  engine  is  running.  To 
explain  the  operation  of  the  Thermostatic  Controlled  Cooling  System, 
those  used  on  the  Cadillac  and  Packard  will  be  described. 

On  the  Cadillac  the  circulation  through  each  cylinder  block  is 
independent  of  that  through  the  other,  two  separate  pumps  being 
provided.  Two  centrifugal  pumps  are  located  at  the  front  end  of 
the  crank  case,  on  each  side,  and  are  driven  from  the  crank  shaft 
through  helical  gears.  A  housing  containing  a  Sylphon  Thermostat 

and  a  valve  controlled  by  the 


Thermostat  are  located  on  the 
cover  of  each  water  pump.  The 
Thermostat  "A"  (Fig.  28)  is 
accordion  shaped.  It  contains 
a  liquid  which  is  converted 
into  gas  when  heated.  The 
resulting  pressure  elongates  the 
Thermostat,  forcing  the  valve 
"B"  from  its  seat.  A  drop  in 
temperature  changes  the  gas  to 
a  liquid,  reducing  the  pressure 
in  the  Thermostat  and  allowing 
it  to  contract,  bringing  the  valve 
"B"  back  to  its  seat. 

When  the  temperature  of 
the  water  in  the  water  jackets 
on  the  cylinders  and  intake 
manifold  is  below  a  predeter- 
mined point  the  valve  "B"  is 
held  tightly  closed  by  the  Ther- 
mostat which  prevents  water  being  drawn  from  the  radiator.  When 
the  temperature  of  the  water  tends  to  rise  above  the  predetermined 
point  the  valve  "B"  is  forced  open  by  the  Thermostat,  permitting 


Fig.  28 — Thermostat  Regulator 
on  Cadillac 


40 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


the  water  pump  "P"  to  draw  water  from  the  radiator.  Provision 
is  made  for  forcing  the  valves  operated  by  the  Thermostat  from 
their  seats.  This  is  necessary  to  drain  the  radiator. 


S      F       K     P     H 


Fig.  29 — Cadillac  Cooling  System 

When  the  engine  is  first  started  and  is  cold  the  valves  operated 
by  the  Thermostats  are  held  tightly  on  their  seats.  This  prevents 
the  water  pumps  from  drawing  water  from  the  radiator.  Under 
these  conditions  the  water  is  circulated  as  follows:  From  the  water 
pump  "P,"  (Fig.  28  and  29)  through  the  hose  "F"  to  the  water 
jackets  on  the  cylinders,  from  the  water  jackets  on  the  cylinders 
some  of  the  water  returns  to  the  pump  "P"  through  the  hose  "C" 
and  the  Thermostat  housing  "E,"  and  the  remainder  is  carried  by  a 
small  pipe  "N"  to  the  water  jacket  around  the  intake  manifold  and 
from  the  intake  manifold  to  the  pump  "P"  through  the  pipe  "D" 
and  the  Thermostat  housing  "E." 

After  the  engine  has  become  warm  and  the  valves  between  the 
pumps  and  radiator  have  been  forced  from  their  seats  by  the  Thermo- 
stats the  circulation  is  as  follows:  Water  is  drawn  from  the  radiator 
through  the  hose  "G"  and  forced  to  the  water  jackets  on  the  cylinders 
through  the  hose  "F,"  from  the  water  jackets  the  water  returns  to 


COOLING  SYSTEMS  41 

the  radiator  through  the  hose  "M"  connecting  the  cylinder  block 
and  radiator.  Water  is  still  forced  to  the  water  jackets  on  the  intake 
manifold  through  the  small  pipe  "N"  and  from  the  intake  manifold 
to  the  pump  "P"  through  the  pipe  "D"  and  the  Thermostat  housing 
"E."  Some  of  the  water  still  flows  back  to  the  pump  through  the 
hose  "C"  and  the  Thermostat  housing  "E." 

As  the  temperature  of  the  water  returning  to  the  pump  through 
the  pipe  "D,"  hose  "C,"  and  Thermostat  housing  "E"  rises  or  falls, 
the  Thermostat  expands  or  contracts,  opening  or  closing  the  valve, 
thereby  admitting  a  larger  or  smaller  amount  of  cooled  water  from 
the  radiator.  A  condenser,  the  purpose  of  which  is  to  prevent  the 
loss  of  the  cooling  medium  by  evaporation  particularly  when  an 
alcohol  solution  is  used,  is  attached  to  the  right-hand  side  of  the 
frame  just  beneath  the  front  floor  boards.  A  pipe  "S"  (Fig.  29) 
connected  to  the  overflow  tube  of  the  radiator  leads  to  the 
condenser. 

The  condenser  acts  in  this  manner.  The  vapor  rising  from  the 
heated  liquid  in  the  radiator  passes  through  the  overflow  tube  to  the 
condenser.  As  it  passes  into  the  liquid  in  the  condenser  the  vapor  is 
condensed.  When  the  engine  has  stopped  the  cooling  of  the  radiator 
and  its  contents  results  in  the  contraction  and  condensation  of  the 
vapor  left  in  the  upper  part  of  the  radiator.  The  partial  vacuum 
thus  caused  allows  the  atmospheric  pressure  in  the  condenser  to 
force  condensed  vapor  back  into  the  radiator.  The  proper  operation 
of  the  condenser  requires  an  air-tight  joint  at  the  radiator  filler  cap. 
To  make  it  possible  to  screw  down  and  tighten  the  cap  without  injury 
to  the  rubber  gasket,  two  metal  washers  are  interposed  between  the 
head  of  the  cap  and  the  gasket.  It  is  important  that  nothing  be 
installed  on  the  radiator  filler  cap  which  might  cause  a  leak  at  the 
cap  or  which  might  make  necessary  the  elimination  of  the  steel 
washers  or  the  cutting  of  a  hole  through  the  rubber  gasket. 

In  the  Thermostatic  Controlled  Cooling  System  as  used  on  the 
Packard  (Fig.  30)  there  are  two  paths  through  which  the  water  may 
circulate.  The  water  is  forced  by  the  pump  through  the  cylinder 
water  inlet  manifold,  thence  through  the  water  jackets,  and  out 
through  the  pipe  at  the  top  of  the  cylinder  block.  From  here  it 
has  two  paths  through  which  it  may  return  to  the  pump.  It  may 
pass  through  the  bypass  manifold  directly  to  the  pump  or  through 
the  radiator  returning  to  the  pump  by  the  lower  pipe. 

The  path  which  the  water  takes  is  regulated  by  the  Thermostat 
which  operates  a  valve  in  the  pipe  leading  to  the  radiator.  The 
operation  of  the  Thermostat  is  identical  with  that  on  the  Cadillac, 
the  only  difference  being  its  location. 


COOLING  SYSTEMS 


43 


The  great  advantage  of  a  Thermostatic  Controlled  Cooling 
System  is  its  efficient  operation  in  cold  weather  in  preventing  cold 
water  being  circulated  through  the  water  jackets  and  cooling  the 
engine  below  an  efficient  running  temperature.  There  is  little  possi- 
bility of  the  radiator  freezing  because  the  length  of  time  required 
to  heat  the  small  quantity  of  water  in  the  jackets  is  very  short.  This 
results  in  sending  a  quantity  of  heated  water  almost  immediately 
into  the  radiator.  The  Thermostat  will  gradually  permit  the 
heating  of  the  water  in  the  entire  system  always  maintaining  the 
water  in  the  jackets  at  approximately  the  same  temperature. 


Fig.  31 — Phantom  View  of  Centrifugal  Pump 

PUMPS.— There  are  several  constructions  of  pumps  used  for 
water  circulation,  the  most  common  of  these  being  the  centrifugal 
and  gear  types.  omer 

In  the  centrifugal 
type  (Fig.  31)  the  water 
enters  at  the  center  of 
the  pump  and  is  caught 
by   the   rotating  blades 
and  thrown  to  the  out- 
side by  centrifugal  force.     .' 
The  casing  limits  its  out-     \ 
ward  motion,  but  allows     \ 
the  blades  to  impel  it  in 
circular  motion,  the  pres- 
sure against  the   casing 
increasing  until  the  out- 
let pipe  is  reached.    Here 
the  resistance  to  its  out-  Fig.  32— Gear  Pump 


44 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


ward  motion  is  removed  and  the  stored-up  energy  forces  the  water 
through  the  discharge  pipe  to  the  water  jackets. 

In  the  gear  pump  (Fig.  32)  the  water  takes  the  path  indicated  by 
the  arrows.  The  gear  teeth  pick  up  the  water  and  carry  it  around  in 
the  spaces  between  the  teeth,  the  pump  casing  making  a  tight  joint. 
The  teeth  of  the  two  gears  meshing  at  the  center  prevent  any  water 
being  carried  down  between  them,  hence  a  steady  stream  of  water 
will  be  forced  out  the  discharge  pipe. 

RADIATORS. — The  purpose  of  a  radiator  is  to  present  a  large 
amount  of  cooling  surface  to  the  air     In  order  to  accomplish  this 


Fig.  33 — Tubular  Radiator  Sections 

there  are  many  constructions  varying  in  design  in  accordance  with 
the  manufacturer's  ideas.    All  radiators  may  be  classed  as  either 

tubular    or    cellular.      The    so- 
called  honeycomb  radiator  may 
,v,,?:  be     either    tubular   or    cellular 
(though  generally  the  latter)  and 
<"-  gets  its  name  from  its  appearance. 
The  tubular  radiator  is  one 
in  which  the  upper  and  lower 
tanks  are  connected  by  a  series 
of  tubes  through  which  the  water 
must  pass.     The  tubes  may  be 
arranged  vertically  or  in  a  zig-zag 
fashion     which    materially    in- 
creases the  cooling  surface. 
Fig.  Z^Tubular  Radiator  In    FJg     33    ^.^    ^^ 

constructions  are  shown,  that  in  the  lower  left-hand  corner  being 
a  honeycomb  type. 


COOLING  SYSTEMS 


45 


In  Fig.  34  a  straight  vertical  tube  type  of  radiator  is  shown  and 
is  typical  of  the  construction  used  for  trucks.  To  increase  the 
radiating  surface  fins  are  employed  on  the  tubes. 

The  cellular  radiator  (Fig.  35)  is  composed  of  a  large  number  of 
individual  air  cells  which  are  surrounded  by  water  and  the  course  of 
the  water  through  the  radiator  is  not  confined  to  any  definite  vertical 


Fig.  35 — Cellular  Radiator  Sections 

or  angular  course.  Because  of  its  appearance  the  cellular  type  is 
usually  known  as  a  "honeycomb"  radiator. 

Since  the  water  passes  through  all  of  the  tubes  of  a  tubular 
radiator,  if  one  tube  becomes  clogged  the  cooling  effect  of  the  entire 
tube  is  lost.  In  the  cellular  construction  the  clogging  of  any  passage 
results  in  a  loss  of  but  a  very  small  part  of  the  total  cooling  surface  as 
compared  to  the  loss  of  a  whole  tube  in  the  tubular  type.  For  this 
reason  the  cellular  or  commonly  called  "  honeycomb "  radiator  is 
more  efficient  but  is  more  expensive  to  construct. 

FANS. — In  order  to  cool  the  water  sufficiently  a  fan  driven  by  a 
belt  or  chain  from  the  engine  is  placed  back  of  the  radiator  so  that 
in  its  operation  it  will  draw  air  through  the  radiator.  In  many  con- 
structions of  radiators  the  mere  motion  of  the  car  could  not  force 
sufficient  air  through  the  radiator  but,  by  placing  a  fan  behind  it, 
sufficient  air  will  be  drawn  through  for  cooling  purposes.  It  is  a 
misinterpreted  idea  that  a  fan  is  used  to  cool  the  engine,  its  function 
being  solely  to  assist  in  cooling  the  water  in  the  radiator.  In  some 
constructions  it  may  assist  slightly  in  cooling  the  engine. 

The  fan  bracket  is  so  constructed  that  the  tension  on  the  belt  is 
adjustable.  At  all  times  the  belt  should  be  under  sufficient  tension 
to  prevent  slippage.  Fans  require  but  little  power  and  usually  run 
at  a  speed  two  or  three  times  as  great  as  that  of  the  crank  shaft  and 
are  mounted  on  ball-bearings  to  reduce  friction  as  much  as  possible. 


46  MOTOR  VEHICLES  AND  THEIR  ENGINES 

ANTI-FREEZING  MIXTURES.— In  order  to  prevent  the  water 
in  the  cooling  system  from  freezing  in  extremely  cold  weather  when 
the  engine  is  not  in  operation  there  is  provided  at  the  bottom  of  the 
radiator,  at  the  lowest  points  in  the  water  jackets,  and  at  the  pump, 
drain  cocks  through  which  the  water  can  be  removed.  Water  in 
freezing  expands  and  if  confined  in  the  cooling  system  would  cause 
the  water  jackets,  pipes,  or  radiator  to  break.  As  an  assurance  in 
freezing  weather  that  the  cooling  system  of  a  car  has  been  drained 
and  as  an  indication  that  it  must  be  filled  before  operating  the  car, 
a  card  marked  DRAINED  in  black  letters  about  three  inches  high 
should  be  conspicuously  displayed.  This  is  usually  done  by  sus- 
pending the  card  across  the  radiator  from  the  filler  cap.  As  it  is 
often  found  undesirable  to  remove  the  water  from  the  cooling  system 
fluids  with  very  low  freezing  points  are  often  employed.  These 
are  called  anti-freezing  mixtures.  The  ideal  requirements  for  an 
anti-freezing  mixture  are  as  follows: 

1.  It  should  cause  no  harmful  effect  to  any  part  of  the  cooling 
system  with  which  it  comes  in  contact. 

2.  It  should  be  easily  dissolved  or  combined  with  water. 

3.  It  should  be  reasonably  cheap. 

4.  It  should  not  waste  by  vaporization,  that  is,  its  boiling  point 
should  be  as  high  as  that  of  water. 

5.  It  should  not  deposit  any  foreign  matter  in  the  jackets  or 
pipes. 

The  materials  which  are  most  commonly  used  are  alcohol,  mix- 
tures of  alcohol  and  glycerine,  kerosene  oil,  and  calcium  chloride. 
The  most  common  of  these  are  solutions  of  alcohol  and  water  in  the 
following  proportions: 

WATER 

80% 
70% 
60% 

The  above  table  is  based  on  the  use  of  denatured  alcohol  but  if 
wood  alcohol  is  used,  slightly  lower  temperatures  can  be  reached  with 
the  same  proportions  of  alcohol  and  water.  In  these  solutions,  the 
alcohol  being  more  volatile  than  water,  will  evaporate  making  it 
necessary  to  continually  add  more  alcohol.  The  use  of  this  solution 
is  very  unsatisfactory  because  the  only  method  of  being  positive  that 
the  alcohol  is  present  is  by  measuring  the  specific  gravity  of  the 
solution. 

There  are  certain  solutions  of  glycerine,  alcohol,  and  water  which 
are  more  stable  because  the  glycerine  holds  the  alcohol  in  solution. 


ALCOHOL 

SPEC.  GRAY. 

FREEZING  POINT 

20% 

.975 

14° 

30% 

.964 

-   1° 

40% 

.954 

-20° 

COOLING  SYSTEMS  47 

The  following  table  shows  the  percentage  of  each  and  the  freezing 
points  of  the  solutions : 

ALCOHOL            GLYCERINE             WATER  FREEZING  POINT 

12%                   12%                   76%  10° 

15%                  15%                  70%  -  5° 

17%                  17%                 66%  -15° 


These  solutions  are  very  satisfactory  as  they  are  dependable,  but 
it  often  happens  that  the  glycerine  will  gum  up  the  radiator  and  stop 
the  circulation  of  the  water  through  some  section  thus  reducing  the 
cooling. 

Calcium  Chloride  or  alkali  solutions  are  often  recommended, 
their  freezing  points  being  very  low.  The  great  objection  to  the  use 
of  these  is  that  they  form  a  scale  in  the  water  jackets  and  radiator 
which  in  time  interferes  with  the  circulation.  When  Calcium 
Chloride  is  used  it  must  be  chemically  pure  as  the  commercial  chloride 
of  lime  sets  up  electrolytic  action.  The  following  solutions  are  used : 

CALCIUM  CHLORIDE    WATER  SPEC.  GRAY.  FREEZING  POINT 

20%  80%  1.119  0° 

22%  78%  1.200  -  9° 

24%  76%  1.219  -18° 


Kerosene  has  the  advantage  of  a  high  boiling  point  so  that  it  does 
not  evaporate  readily  but  it  has  the  disadvantage  of  not  making  a 
good  mixture  with  water  and  will  not  absorb  heat  as  rapidly.  Kero- 
sene should  not  be  used  where  there  is  any  rubber  in  the  system  for 
it  attacks  the  rubber  hose  and  gaskets  and  causes  them  to  deteriorate 
rapidly. 

Whenever  an  anti-freezing  mixture  is  used  it  is  essential  that  it 
be  removed  from  the  cooling  system  as  soon  as  the  weather  moderates. 
If  this  is  not  done  the  engine  will  overheat. 

If  the  water  in  the  cooling  system  should  freeze  through  neglect 
of  ordinary  precaution  do  not  attempt  to  thaw  it  by  starting  the 
engine,  but  thaw  by  putting  the  car  in  a  warm  place  or  by  draining 
the  system  and  then  adding  hot  water.  It  has  been  stated  that 
solutions  of  Calcium  Chloride  deposit  a  scale  in  the  water  jackets 
and  radiator  and  therefore  should  not  be  used.  There  are  many 
places  in  which  the  drinking  water  contains  a  considerable  amount 
of  lime  which  will  cause  the  same  result.  To  prevent  scale  it  is 
always  best  to  fill  the  cooling  system  with  rain  water. 


CHAPTER  VI 


FUEL  FEED  SYSTEMS 

Provision  must  be  made  on  motor-propelled  vehicles  for  storing 
gasoline  and  supplying  it  to  the  carburetor.  There  are  three  systems 
in  common  use  for  supplying  liquid  fuel  to  the  carburetor  from  the 
storage  tank,  the  Gravity  System,  the  Force  Feed  System,  and  the 
Vacuum  System. 

GRAVITY  SYSTEM.— In  the  gravity  fuel  feed  system  the  storage 
tank  must  be  placed  above  the  carburetor  so  that  the  gasoline  will 
flow  from  it  to  the  carburetor  by  gravity.  A  typical  system  of  this 
kind  is  shown  in  Fig.  36.  It  is  very  simple  and  has  but  a  few  parts. 
The  storage  tank  has  a  filler  cap  in  the  top  with  an  air  vent  through 
it  and  a  gasoline  outlet  at  the  bottom  which  leads  to  a  sediment  well 


r.ASOLINE    TAKK    COVCR 
SHUT  OFF.  VALVE. 


AUXILIARY    AIR 
ADJUSTMENT 

THROTTLE  LEVER 
.BELL-CRANK 

OPERATING 
A ;o-  IN  TAKE  VALVE 

ruOAT-CHAMBER  CAP. 
•  LOW   SPEED 

ADJUSTMENT 


GASOLINE   »MD  OPE 


Fig.  36 — Gravity  Fuel  Feed  System 

and  drain  plug.  The  feed  pipe  to  the  carburetor  takes  off  from  the 
top  of  this  well  and  is  as  straight  and  short  as  possible.  A  stop  cock 
for  shutting  off  the  supply  of  gasoline  from  the  tank  is  provided  in 
the  outlet  underneath  the  tank  or  a  needle  valve  is  used  inside  the 
tank  which  can  be  controlled  from  the  top.  Automatic  gauges  are 
sometimes  provided  on  the  storage  tank  to  show  the  amount  of  fuel 
in  the  tank. 

Because  of  the  simplicity  of  construction  they  are  not  apt  to  get 
out  of  order.  On  the  other  hand  they  have  several  drawbacks. 
The  pressure  varies  with  the  relative  height  of  tank  and  carburetor 
and  since  this  is  usually  not  very  great  the  resulting  pressure  will  be 
low.  When  ascending  or  descending  grades  the  relative  height  of 
tank  and  carburetor  will  change  which  correspondingly  varies  the 
pressure.  Since  the  tank  must  be  above  the  carburetor  for  this 

48 


FUEL  FEED  SYSTEMS  49 

system  to  be  operative  its  location  is  very  limited  and  it  generally 
has  to  be  placed  at  some  point  not  readily  accessible.  This  fact  also 
makes  it  hard  to  shut  off  the  supply  of  gasoline  and  in  case  fire  occurs 
at  the  carburetor.  The  result  may  be  serious  if  the  supply  of  gasoline 
is  not  immediately  shut  off. 

PRESSURE  SYSTEM.— When  the  pressure  fuel  feed  system  is 
employed  the  storage  tank  may  be  placed  at  the  most  convenient 
and  accessible  point  on  the  machine  usually  at  the  extreme  rear  of 
the  chassis.  When  installed  in  this  manner  it  is  necessary  to  force 
gasoline  out  of  the  tank  by  air  pressure  since  the  gasoline  tank  is 
lower  than  the  carburetor.  Pressure  is  maintained  by  a  small  air 
pump  automatically  controlled  and  driven  by  the  engine.  An 
auxiliary  hand  pump  gives  enough  initial  pressure  to  force  gasoline 
to  the  carburetor  for  starting.  A  safety  valve  in  the  pressure  system 
prevents  the  pressure  from  rising  beyond  a  safe  limit.  The  tank  must 
be  airtight  and  the  filler  cap  screwed  tight  with  a  wrench  to  hold  the 


Fig.  37 — Pressure  Fuel  Feed  System 

pressure.  A  gasoline  gauge  is  provided  to  show  how  much  gasoline 
the  tank  contains.  Two  pipes  run  from  the  tank,  one  being  the 
pressure  line  and  the  other  the  gasoline  line  (Fig.  37).  The  gasoline 
line  runs  from  the  lowest  point  in  the  tank  directly  to  the  carburetor. 
The  pressure  line  is  connected  to  both  the  engine  driven  pump  and 
the  hand  pump.  The  hand  pump  is  shut  off  by  means  of  a  valve  at 
its  lower  end  when  not  in  use.  A  pressure  gauge  may  be  attached 
to  this  line  near  the  hand  pump  to  show  the  pressure  in  the  system 
at  all  times.  Some  systems  have  the  pressure  gauge  attached  to  the 
gasoline  line. 

Since  a  constant  pressure  is  maintained  in  the  tank  at  all  times 
the  gasoline  is  fed  uniformly  to  the  carburetor  and  its  flow  is  inde- 
pendent of  the  relative  position  of  tank  and  carburetor.  In  addition 
to  this  the  location  of  the  tank  is  not  limited,  permitting  it  to  be 


50 


FUEL  FEED  SYSTEMS  51 

o* 

placed  in  an  accessible  position  where  gasoline  may  be  put  in  with  the 
greatest  facility.  Should  fire  occur  at  the  carburetor  the  supply  of 
gasoline  can  immediately  be  shut  off  at  the  dash  by  turning  the  cock 
at  the  hand  pump  so  that  the  pressure  in  the  system  can  escape  to 
the  air.  Trouble  may  be  experienced  in  this  system  with  leaks  in  the 
various  pipes,  valves,  or  filler  cap  and  the  pumps  must  be  in  proper 
working  order  for  constant  operation.  In  addition  the  pressure  is 
liable  to  interfere  with  the  operation  of  the  carburetor  float  and 
prevent  the  needle  valve  from  seating  properly.  However,  the  pressure 
feed  system  has  been  so  highly  perfected  that  few  mechanical  diffi- 
culties are  apt  to  be  experienced. 

VACUUM  SYSTEM.— In  this  system  the  gasoline  is  drawn  from 
a  supply  tank  in  the  rear  of  the  car  by  suction  to  a  small  auxiliary 
vacuum  tank  near  the  engine  from  which  it  flows  by  gravity  to  the 
carburetor.  The  vacuum  tank  is  installed  under  the  hood  and  con- 
nected by  tubing  to  the  intake  manifold,  gasoline  storage  tank,  and 
carburetor  (Fig.  38).  The  suction  created  by  the  pistons  on  their 
outward  strokes  in  the  engine  causes  a  suction  in  the  vacuum  tank 
through  the  connection  to  the  intake  manifold.  This  draws  gasoline 
from  the  main  supply  tank  into  the  vacuum  tank  through  the  tubing 
from  the  gasoline  supply  tank. 

The  Stewart  Vacuum  Gasoline  Tank  consists  of  two  chambers. 
The  upper  is  the  filling  chamber  and  the  lower  is  the  emptying 
chamber.  Between  these  two  chambers  is  a  partition  in  which  is 
placed  a  valve.  The  suction  of  the  pistons  on  the  intake  stroke 
creates  a  vacuum  in  the  upper  chamber  and  this  vacuum  closes  the 
valve  between  the  two  chambers  and  also  sucks  or  pumps  up  the 
gasoline  from  the  main  supply  tank  into  this  upper  chamber.  As  the 
gasoline  flows  into  this  upper  chamber  it  raises  a  float.  When  the 
float  has  risen  to  a  certain  point,  it  operates  a  valve  which  shuts  off 
the  suction  and  at  the  same  time  opens  an  air  valve.  This  admission 
of  outside  air  releases  the  vacuum  causing  the  valve  leading  into  the 
lower  chamber  to  open,  through  which  the  gasoline  immediately 
commences  to  flow  into  the  lower  or  emptying  chamber.  This  lower 
chamber  is  always  open  to  the  outside  air  so  that  nothing  can  ever 
prevent  the  gasoline  in  it  from  feeding  through  its  connection  to  the 
carburetor  in  an  uninterrupted  flow. 

DESCRIPTION  OF  STEWART  VACUUM  TANK 

"A"  is  the  suction  valve  for  opening  and  closing  the  connection 
to  the  manifold  and  through  which  a  vacuum  is  extended  from  the 
engine  manifold  to  the  gasoline  tank, 


AIR' 


FROM 

GASOLINE 
SUPPLY  TANK 


TO  CARBU- 
RETOR 


Fig.  39 — Stewart  Vacuum  Tank 

52 


FUEL  FEED  SYSTEMS  53 

"B  "  is  the  atmospheric  valve  and  permits  or  prevents  atmospheric 
pressure  in  the  upper  chamber.  When  the  suction  valve  "A"  is 
open  and  the  suction  is  drawing  gasoline  from  the  main  reservoir 
this  atmospheric  valve  "B"  is  closed. 

"C"  is  the  pipe  connecting  the  tank  to  manifold  of  the  engine. 

"D"  is  the  pipe  connecting  the  vacuum  tank  to  main  gasoline 
supply  tank. 

"E"  is  the  lever  to  which  the  two  coil  springs  "S"  are  attached. 
This  lever  is  operated  by  the  movement  of  the  float  "G." 

"F"  is  a  short  lever  which  is  operated  by  the  lever  "E"  and 
which  in  turn  operates  the  valves  "A"  and  "B." 

"G"  is  the  float. 

"H"  is  the  flapper  valve  in  the  outlet  "T"  (Fig.  39).  This 
flapper  valve  is  held  closed  by  the  action  of  the  suction  whenever 
the  valve  "A"  is  open,  but  it  opens  when  the  float  valve  has  closed 
the  vacuum  valve  "A"  and  opened  the  atmospheric  valve  "B." 

"J"  is  a  plug  in  the  bottom  of  the  tank  which  can  be  removed 
for  draining  or  cleaning  the  tank.  This  plug  can  be  replaced  with  a 
pet  cock  to  be  used  for  drawing  off  gasoline  for  priming  or  cleaning 
purposes. 

"K"  is  the  line  to  the  carburetor  extended  on  inside  of  the  tank 
to  form  a  pocket  for  trapping  water  and  sediment. 

"L"  is  the  channel  space  between  the  inner  and  outer  shells  and 
connects  with  the  air  vent  "R,"  thus  maintaining  an  atmospheric  pres- 
sure in  lower  chamber  at  all  times.  This  insures  an  even  flow  of 
gasoline  to  the  carburetor. 

"R"  is  an  air  vent  over  the  atmospheric  valve.  The  effect  of 
this  is  the  same  as  if  the  whole  tank  were  elevated  and  is  for  the  pur- 
pose of  preventing  an  overflow  of  gasoline  if  the  storage  tank  became 
higher  than  the  vacuum  tank.  Through  this  tube  also  the  lower  or 
reservoir  chamber  is  continually  open  to  atmospheric  pressure  so 
that  the  flow  of  gasoline  from  this  lower  chamber  to  the  carburetor 
is  always  an  uninterrupted  flow.  This  outlet  is  located  at  the  bottom 
of  the  float  reservoir  in  which  is  the  flapper  valve  "H." 

The  simple  durable  construction  used  in  the  manufacture  of  the 
Stewart  Vacuum  Tank  makes  it  unlikely  that  it  will  ever  be  neces- 
sary to  make  internal  repairs.  However,  some  of  the  following 
troubles  may  possibly  be  experienced.  The  vent  tube  may  overflow 
and  if  it  does  this  regularly  the  trouble  may  be: 

1.  The  air  hole  in  main  gasoline  tank  filler  cap  may  be  too  small 
or  may  be  stopped  up. 

2.  Vacuum  tank  may  not  be  placed  high  enough  above  the 
carburetor. 


54  MOTOR  VEHICLES  AND  THEIR  ENGINES 

If  faulty  feed  is  due  to  the  vacuum  system  it  may  result  from  one 
of  the  following  causes: 

1.  Gasoline  strainer  may  be  clogged  and  should  be  examined 
first  if  the  tank  fails  to  operate. 

2.  The  float  may  leak  allowing  gasoline  to  be  drawn  into  the  mani- 
fold which  will  choke  down  the  engine. 

3.  Flapper  valve  may  not  seat  properly. 

4.  Manifold  connection  may  be  loose  allowing  air  to  be  drawn 
into  it. 

5.  Tubing  may  have  become  stopped  up. 

This  system  supplies  gasoline  at  a  constant  pressure  but  low 
enough  not  to  interfere  with  the  action  of  the  carburetor  float.  This 
system  does  not  limit  the  location  of  the  supply  tank  but  eliminates 
the  trouble  giving  pumps  and  valves  of  the  pressure  system  and 
permits  the  final  supply  of  gasoline  to  the  carburetor  by  gravity. 

CARE  OF  GASOLINE. — Gasoline  being  a  volatile  liquid  is  very 
dangerous  if  not  properly  handled  but  is  quite  safe  if  the  proper 
precautions  are  taken.  It  should  never  be  exposed  in  a  closed  room 
as  it  will  evaporate,  mixing  with  air  and  forming  an  explosive  gas. 
Open  lights  should  never  be  used  where  gasoline  vapor  is  apt  to  be 
encountered.  When  it  is  necessary  to  handle  gasoline  at  night  in 
the  open  an  electric  light  should  be  used  and  under  no  circumstances 
should  a  flame  be  brought  near  the  gasoline.  When  an  open  flame  is 
used  at  some  distance  from  gasoline,  it  should  always  be  placed  above 
the  gasoline.  Gasoline  should  be  stored  in  an  underground  tank  or 
in  an  air-tight  container  in  a  separate  building  used  especially  for 
that  purpose. 

In  putting  out  a  gasoline  fire,  water  should  never  be  used  as  the 
gasoline,  being  lighter  than  water,  floats  on  it,  resulting  in  spreading 
the  fire.  The  only  successful  method  of  extinguishing  a  gasoline 
fire  is  to  smother  it  with  sand,  sawdust,  or  a  blanket  or  by  the  use  of 
a  chemical  fire  extinguisher.  Each  piece  of  motor  equipment  should 
be  provided  with  a  small  chemical  extinguisher  for  this  purpose. 


CHAPTER  VII 


FUELS 

The  crude  oils  from  which  gasoline  is  derived  occur  in  various 
parts  of  the  world  and  manifest  a  variety  of  properties.  Thus  the 
"paraffine  base,"  Pennsylvania  and  Ohio  oils  yield  60  to  70  percent 
of  kerosene  and  lubricating  oils,  while  the  "asphaltum  base,"  Cali- 
fornia, Oklahoma,  or  Texas  oil,  furnishes  practically  nothing  of  either 
of  these  products.  It  is  much  heavier  than  Pennsylvania  oil,  and 
Mexican  oil  is  usually  still  heavier.  Crude  oils  having  an  asphaltum 
base  are  heavy  and  dark-colored  and  when  distilled  down  leave  a 
black  tarry  residue.  If  a  crude  oil  has  a  paraffine  base  it  is  lighter 
in  weight  and  color,  and  the  residue  after  distillation  yields  (by 
pressure  and  refrigeration)  the  white  paraffine  wax.  Either  kind  of 
crude  oil  will  yield  good  gasoline.  A  large  proportion  of  the  world's 
supply  of  crude  petroleum  comes  from  American  wells.  These 
variations  are  indicated  by  the  density,  which  varies  from  a  maximum 
of  50°  with  Pennsylvania  crude  down  to  12°  or  less  with  California 
crude.  The  lower  the  density,  the  less  is  the  proportion  of  gasoline 
obtainable  from  the  crude  oil. 

The  density  of  liquids  lighter  than  water  (like  fuel  oils  and  their 
products)  is  indicated  by 

140 
specific  gravity  = 

where  B  is  the  hydrometer  reading.  The  specific  gravity  is  the  weight 
of  the  liquid  as  compared  with  the  weight  of  an  equal  bulk  of  water. 
Hence  water  would  give  an  hydrometer  reading  of  10°.  Water 
weighs  8^  Ibs.  per  gallon  at  normal  temperature. 

Crude  oils  are  too  heavy  and  viscious  for  use  as  fuels  in  internal 
combustion  engines  without  special  preparatory  treatment.  They 
require  heating  and  may  liberate  poisonous  or  explosive  gases  which 
are  heavier  than  air.  They  contain,  as  impurities,  free  carbon, 
sulphur,  silt,  and  moisture,  in  widely  varying  proportions. 

When  crude  oil  is  subjected  to  moderate  heat  those  of  its  con- 
stituents which  have  low^boiling  points  are  boiled  off.  By  condensing 
their  vapors,  highly  inflammable  gasoline  is  obtained.  After  this  a 
somewhat  higher  temperature  may  be  applied  and  lower  grade 
gasoline  collected  in  a  separate  condenser.  By  successive  increases 

55 


56 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


GAS61WC.  B£MZ/*/C,  AW 


of  temperature,  with  separa- 
tion of  products  condensed,  a 
considerable  series  of  products 
is  derived. 

It  would  be  commercially 
inadmissible  to  treat  crude  oil 
with  a  view  to  deriving  gaso- 
line only.  This  process  is 
called  "fractional  distillation," 
and  is  the  basis  of  petroleum 
refining.  As  the  temperature 
of  distillation  increases,  the 
products  become  lighter  (hav- 
ing a  higher  hydrometer  read- 
ing and  less  fluid  and  inflammable.  Fig.  40  shows  the  composition 
of  a  sample  of  American  crude  oil. 


Fig.  40 — Composition  of  Crude  Oil 


AVERAGE  FRACTIOXATION  OF  CRUDE  PETROLEUMS   (ROBINSON) 

AMERICAN  OIL 


CONSTITUENT 

PERCENT. 
OBTAINED 

BOILING 
POINT,  DEG. 
FAHR. 

HYDROMETER 
READING, 
DEG. 

Gasoline          

0-10 

32-265 

58-107 

Kerosene  

12-55 

300-700 

44-49 

Fuel  oil  (gas  oil)  

variable 

35 

Lubri  eating  oil 

17^ 

22-28 

Paraffin  and  residue 

2-10 

RUSSIAN  OIL 


Gasoline  

5-16 

53-63 

Kerosene 

40-52 

33-41 

Lubricating  oil 

3-40 

22-31 

Residue  (fuel  oil)                ...    . 

10-15 

17-25 

The  boiling  point  of  any  liquid  varies  according  to  the  pressure 
to  which  it  is  subjected.  If  the  boiling  temperature  at  atmospheric 
pressure  is  less  than  the  resisting  temperature,  the  liquid  will  vaporize 
until  a  pressure  is  created  equal  to  that  at  which  boiling  occurs  at  the 
existing  temperature.  The  lighter  gasolines  therefore  are  always 
boiling  off  from  the  crude  oils  which  contain  them.  Loss  and  danger 
can  be  avoided  only  by  confining  such  oils. 


FUELS 


57 


PRESSURES  AND  BOILING  POINTS 


Boiling  Point,  Deg.  Fahr  

70 

80 

90 

100 

110 

120 

140 

Pressure,  f  Ordinary  gasoline  
inches     I  Kerosene,  poor*  

8.9 
1.0 

10.0 
1.2 

11.8 
1.4 

13.8 
1.5 

16.4 
1.6 

19.6 
1.8 

2^3 

of                            ordinary  

0.6 

0.7 

0.8 

0.9 

1.1 

1.3 

1.7 

Mercury  [                   water  white.  .  . 

0.6 

0.6 

0.6 

0.7 

0.7 

0.8 

1.0 

*Poor  for  use  as  an  iUuminant,  because  volatile  and  therefore  unsafe.  The 
most  dangerous  illuminating  kerosenes,  are,  however,  the  best  as  fuels  for  internal 
combustion  engines. 

To  convert  pressure  in  inches  of  mercury  to  Ib.  per  sq.  in.,  mul- 
tiply by  0.49.  Thus,  if  gasoline  is  vaporized  at  120°  F.  its  vapor 
pressure  is  9.6  Ib.  per  sq.  in.  The  lower  the  pressure,  the  lower  the 
temperature  at  which  vaporization  occurs.  Suction,  therefore, 
facilitates  carburetion. 

The  proportions  of  the  various  products  obtainable  from  re- 
fining any  particular  crude  oil  cannot  be  changed  by  the  refiner. 
In  getting  5  percent  of  gasoline,  for  example,  he  is  compelled  to 
accept  40  percent  of  kerosene,  say.  If  the  demand  for  kerosene  is 
slight,  while  the  demand  for  gasoline  is  brisk,  he  may  have  to  sell 
the  former  at  a  loss  and  protect  himself  by  charging  an  excessive 
price  for  gasoline.  There  is  no  such  thing  as  "cost  of  production11 
chargeable  against  any  one  of  the  products.  When  any  one  is  cheap, 
others  must  be  dear.  If  gasoline  is  cheap  at  any  time  it  is  because 
there  is  relatively  a  greater  demand  for  other  products.  About  1903 
kerosene  was  cheaper  than  gasoline  in  some  sections.  Recently  it 
has  been  twice  as  costly. 

The  average  gasoline  consists  mainly  of  carbon  and  hydrogen: 
From  83J^  to  85  parts  of  the  former  to  15  to  15 J^  of  the  latter  by 
weight.  Good  commercial  gasoline  should  show  an  hydrometer  read- 
ing between  67°  and  73°.  Grades  down  to  50°  are  sometimes  offered. 
They  are,  of  course,  not  true  gasoline,  but  may  be  used  in  warm 
weather  without  difficulty.  This  density  is  about  the  same  as  that 
of  some  of  the  best  samples  of  Pennsylvania  crude  oil.  At  68°  the 
specific  gravity  is  140 -^  198  =  0.71.  Since  water  weighs  8.33  Ib.  per 
gal.,  this  gasoline  weighs  0.71X8.33  =  5.91  Ib.  per  gal.  Petroleum 
products  are  always  sold  by  bulk;  the  gallon  or  the  42-gal.  barrel. 
It  would  be  fairer  if  they  were  sold  by  weight. 

The  weight  per  measured  gallon  is  an  exact  indication  of  the 
density.  If  w  =  weight  per  gallon,  B  =  hydrometer  density,  then 

1  -t  r>rj 

B  =  -      -130.     Thus  if  the  weight  per  gallon  is  5.835  Ib.,  B  =  70°. 
It  will  be  noted  that  some  slight  amounts  of  the  lighter  gasolines 


58  MOTOR  VEHICLES  AND  THEIR  ENGINES 

are  obtained  by  distillation  at  temperatures  as  low  as  32°  F.;  i.e., 
without  any  heat  at  all.  In  fact,  as  much  as  IK  percent  of  some 
American  crude  oils  will  distil  off  at  temperatures  below  150°  F. 
These  products  are  highly  inflammable  and  dangerous.  It  is  not 
always  possible  to  market  them.  By  blending  them  with  rather  light 
kerosene  a  substance  is  produced  which  may  be  regarded  as  gasoline, 
for  it  has  the  density  of  the  latter.  It  has  different  properties,  how- 
ever, notably  with  respect  to  igniting  point  and  vapor  pressure. 

Gasoline  may  be  produced  from  natural  gas  by  the  combined 
effects  of  pressure  and  cooling.  Improved  methods  of  distillation 
(Burton  and  Rittman  processes,*  etc.)  increase  the  gasoline  yield 
from  crude  oil,  but  usually  at  the  cost  of  some  impairment  to  quality. 

Average  gasoline  must  be  supplied  with  air  in  the  ratio  15  to  1 
by  weight  for  complete  combustion.  This  means  that  1  Ib.  of  fuel 
requires  200  cu.  ft.  of  air  at  62°  F.  Gasoline  vapor  weighs  0.24  Ib. 
per  cu.  ft.  at  atmospheric  pressure  and  32°  F.,  or  is  about  three  times 
as  heavy  as  air.  About  50  cu.  ft.  of  air  are  required  to  make  a 
perfect  combustible  mixture  with  1  cu.  ft.  of  gasoline  vapor.  These 
ratios  may  be  considerably  varied  without  preventing  ignition,  but 
if  varied  the  power  and  efficiency  are  influenced  unfavorably. 
According  to  Lucke,  limits  are  as  follows: 

RATIO  OP  GASOLINE  VAPOR  TO 
TOTAL  MIXTURE,  BY  VOLUME 

86°  Gasoline "          0.0154  to  0.0476 

71°  Gasoline 0.0154  to  0.0476 

65°  Gasoline 0.0131  to  0.0476 

If  these  limits  are  passed,  the  mixture  will  not  ignite  explosively 
(at  atmospheric  pressure,  by  electric  spark).  As  has  been  shown, 
the  best  value  is  about  &  or  0.02.  A  rich  mixture  causes  failure  to 
ignite  less  promptly  than  does  a  weak  mixture. 

The  heat  value  of  a  fuel  is  expressed  in  British  thermal  units 
(B.  t,  u.).  One  B.  t.  u.  is  the  quantity  of  heat  necessary  to  raise 
the  temperature  of  1  Ib.  of  water  1°  F.  It  is  equivalent  to  778  ft.  Ib. 
of  mechanical  energy.  Since  1  horse  power  =  33,000  ft.  Ib.  per  min., 
it  is  also  equal  to  33,000 -f- 778  =  42.42  B.  t.  u.  per  min.  Average 
gasoline  contains  from  19000  to  21000  B.  t.  u.  per  Ib.  In  general, 
for  all  petroleum  distillates, 

B.  t.  u.  per  lb.  =  18650+40  (B-10). 
Thus  for  68    gasoline,  B.  t.  u.  per  lb.  =  20970.     The  lighter  the  dis- 


*The  Burton  process  involves  the  obtaining  of  gasoline  by  redistillation  of 
less  volatile  products  under  pressure.  The  Rittman  process,  developed  by  the 
United  States  Bureau  of  Mines,  is  similar,  but  the  operation  is  conducted  con- 
tinuously instead  of  in  batches. 


FUELS  59 

tillate  the  higher  the  heat  value.  One  horse  power  is  42.42  B.  t.  u. 
per  min.  or  42.42X60  =  2545  B.  t.  u.  per  hr.  The  gasoline  con- 
sumption of  a  perfect  engine  would  be  2545 -T- 20970  =  0.121  Ib.  per 
hour  per  horse  power.  Actually  it  is  four  to  seven  times  this  or  more, 
on  account  of  the  inefficiency  of  the  engine.  High  compression — 
which  follows  low  clearance — reduces  the  fuel  consumption. 

The  fuel  consumed  per  mile  depends  on  the  traction  force  exerted, 
the  efficiency  of  engine  and  driving  mechanism,  and  the  speed.  If 
p  =  average  pressure  in  the  cylinder  during  the  power  stroke,  d  = 
diameter  of  cylinder  and  n  the  number  of  cylinders,  the  total  pressure 
continuously  maintained  in  a  four-cycle  engine  is  P  =  ?rd2np.  If 
the  stroke  is  s  and  the  engine  makes  r  rev.  per  min.,  and  if  the 
efficiency  from  cylinder  to  wheels  is  e,  the  horse  power  exerted  at  the 
wheels  if  H  =  Pesr-J- 198000.  If  the  gear  ratio  is  g  (engine  speed 
divided  by  wheel  speed)  and  the  wheel  diameter  is  D  in.,  the  speed 
of  the  truck  is  V  =  nDr  ^- 1056  g.  The  tractive  force  is  T  =  375  H  + 
V  =  2  Pesg-r-7rD,  which  is  practically  independent  of  the  engine 
speed.  Take  p  =  70,  d  =  5,  n  =  4 :  then  P  =  1375.  Take  s  =  7,  r  =  700, 
e  =  0.70.  Then  H  =  23.8.  Take  g  =  5,  D  =  34:  then  V=14.2  miles 
per  hour,  and  T  =  629  Ibs.  When  working  at  full  traction,  H  is 
about  nd2-j-2.5  and  the  fuel  consumption  about  0.7  H  Ib.  per  hour. 

If  gasoline  is  used  composed  of  84  parts  of  carbon  to  16  of  hydro- 
gen, by  weight,  about  15.22  Ibs.  of  air  will  be  the  correct  amount  per 
Ib.  of  fuel.  More  air  will  give  more  power,  but  at  a  sacrifice  of 
efficiency.  Suppose  the  truck  to  make  5  miles  per  gallon  of  gasoline. 
If  the  liquid  fuel  were  stretched  out  along  the  road  in  a  pipe,  the  tube 
of  fuel  containing  one  gallon  or  231  cubic  inches  would  be  5  miles  or 
316800  inches  long,  and  its  diameter  would  be  about  %3  of  an  inch. 
A  similar  pipe  full  of  air  would  contain  1130  cu.  ft.,  or  the  diameter 
would  be  2.8  inches.  This  illustrates  the  point  that  most  of  what 
goes  into  the  cylinder  under  any  condition  is  nothing  but  air. 

Since  1  Ib.  of  gasoline  produces  about  200  cu.  ft.  of  combustible 
mixture,  the  mixture  contains  about  20970 -T- 200  =  105  B.  t.  u.  per 
cu.  ft.  This  is  reduced  if  the  temperature  is  higher  than  62°  F., 
because  200  cu.  ft.  at  62°  F.  will  occupy  a  larger  volume  at  higher 
temperatures. 

Efforts  are  constantly  being  made  to  find  acceptable  substitutes 
for  gasoline.  The  most  important  substitutes  may  be  grouped  in 
three  classes:  Lower  grade  distillates,  including  kerosene;  alcohol; 
and  coal-distillation  products,  such  as  benzol.  The  study  of  sub- 
stitutes has  until  recently  been  carried  on  much  more  thoroughly  in 
Europe  than  in  this  country,  because  there  are  no  readily  accessible 
supplies  of  gasoline  from  the  commercial  centers  of  the  continent. 


60 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


KEROSENE  has  very  nearly  the  same  percentage  composition 
as  gasoline,  but  its  density  being  greater,  its  heat  value  is  less.  It 
requires  more  air  for  combustion,  and  the  heat  value  per  cu.  ft.  of 
combustible  mixture  is  less.  The  lower  heat  value  is  not  an  objection  ; 
in  fact,  it  is  in  one  way  an  advantage.  Low  heat  values  mean  a  high 
igniting  temperature.  This  permits  of  more  compression  without 
danger  of  pre-ignition,  and  high  compression  increases  both  power 
and  efficiency.  However,  a  high  ignition  temperature  does  itself 
introduce  difficulties. 

The  essential  objection  to  kerosene  is  the  difficulty  of  vaporizing 
it.  The  table  shows  that  its  boiling  point  is  300°  F.  or  more.  Gas- 
oline may  be  vaporized  either  by  pure  evaporation  in  a  slow  current 
of  warm  air,  or  by  spray-injection.  Kerosene  needs  heat.  This 
may  be  supplied  externally,  at  the  carburetor;  or  the  fuel  may  be 
delivered  to  the  cylinder  in  liquid  form  by  a  pump  and  vaporized  by 
contact  with  a  hot  (un jacketed)  cap  or  plate  forming  a  part  of  the 
cylinder.  This  is  the  method  of  the  Hornsby-Akroyd  stationary 
engine,  but  the  timing  of  ignition  is  uncertain,  especially  under 
variable  loads.  For  motor  cars,  carburetor  heating  is  more  prom- 
ising. 

Kerosene  is  not  necessarily  more  apt  to  form  carbon  deposits. 
These  will  result  from  any  blended  fuel  in  which  the  free  carbon  of 
the  heavier  constituents  has  not  been  thoroughly  filtered  out,  or 
from  any  fuel  at  all  under  appropriate  conditions  of  carburation  and 
cooling. 

Alcohol  as  a  fuel  has  had  considerable  attention.  There  are  two 
kinds,  methyl  or  wood  alcohol,  and  ethyl  or  grain  alcohol.  The 
former  contains  half  the  carbon  and  two-thirds  the  hydrogen  of  the 
latter.  It  has  only  about  three-fourths  the  heat  value  and  requires 
less  air  for  combustion.  Unlike  petroleum  distillates,  both  of  the 
alcohols  contain  oxygen.  Commercial  alcohols  always  contain  water. 
This  does  not  destroy  their  value  as  fuels.  The  following  table 
shows  the  effect.  The  B.  t.  u.  per  Ib.  are  adjusted  values,  which 


Percent  of  Alcohol  in  Mixture, 
by  Weight  

93  8 

87  8 

81  8 

76  1 

70  5 

65  0 

Specific  Gravity  

0.805 

0  815 

0  826 

0  836 

0  846 

0  856 

B.  t.  u.  per  Ib  

10880 

10080 

9360 

8630 

7920 

7200 

are  comparable  among  themselves,  but  not  with  those  given  for 
petroleum  distillates.  For  the  latter  purpose,  the  heat  value  of  pure 
ethyl  alcohol  may  be  taken  at  12800  B.  t.  u.  per  Ib.  Denatured 
alcohol  is  a  mixture  of  pure  ethjrl  alcohol,  90  parts;  water,  10  parts; 


FUELS  61 

methyl  alcohol,  10  parts;  and  benzine,  J/£  part;  by  volume.  Alter- 
natively, the  last  two  constituents  may  be  replaced  by  methyl  alcohol, 
2  parts,  and  pyridin  bases,  Y^  part.  Denaturing  makes  alcohol  unfit 
for  use  in  connection  with  beverages. 

One  cubic  foot  of,  alcohol  vapor  requires  14J/£  cu.  ft.  of  air  for 
complete  combustion.  It  will  ignite  when  the  air  volume  is  any- 
where between  7  and  25  cu.  ft.  If  the  air  supply  is  seriously  deficient, 
the  combustion  products  will  contain  acetic  acid,  which  causes 
rusting  and  corrosion.  The  igniting  temperature  of  alcohol  vapor  at 
atmospheric  pressure  is  950°  F.  The  alcohols  are  intermediate 
between  gasoline  and  kerosene  in  their  readiness  of  vaporization, 
and  methyl  alcohol  is  particularly  close  to  gasoline  in  its  vaporizing 
properties.  Moderate  heating  at  the  carburetor  is  required  in  cold 
weather.  Higher  compression  is  necessary  than  with  gasoline,  for 
the  same  power  and  efficiency,  and  the  engine  must  be  specially 
designed  for  such  high  compression.  Tests  have  shown  that  where 
70  Ibs.  compression  pressure  was  used  for  both  fuels,  the  alcohol 
engine  consumed  50  percent  more  fuel  than  that  burning  gasoline. 
By  raising  the  compression  of  the  former  engine  to  180  Ibs.,  its  fuel 
consumption  became  the  same  as  that  of  the  gasoline  engine:  0.10 
gallon  per  hour  per  horse  power.  Unfortunately  the  present  methods 
for  distillation  of  alcohol  from  vegetable  substances  have  not  yet 
produced  that  fuel  at  a  price  competitive  with  that  of  gasoline. 

Benzol  is  a  by-product  of  the  distillation  of  soft  coal,  for  the 
manufacture  of  coal  gas  or  coke.  It  appears  both  in  the  gas  and  in 
the  liquid  tar,  and  is  derived  only  when  by-products  or  retort  ovens 
are  used.  It  ignites  at  970°  F.  at  atmospheric  pressure.  Its  specific 
gravity  is  0.88  and  its  heat  value  about  18000  B.  t.  u.  per  Ib.  About 
13}/£  Ib.  of  air  are  required  for  combustion  of  1  Ib.  of  benzol,  or  about 

36  cu.  ft.  of  air  for  1  cu.  ft.  of  benzoL     Ignition  is  possible  with  15  to 

37  volumes  of  air,  but  weak  mixtures  are  very  uncertain.     Benzol 
has  been  used  in  three  ways.     While  somewhat  less  volatile  than 
gasoline,  it  has  been  vaporized  in   an   ordinary  carburetor,  after 
starting  on  gasoline.     By  adding  benzol  to  alcohol  there  is  less  danger 
of  corrosion  from  acetic  acid  formation.     In  Europe,  a  mixture  of 
equal  parts  of  benzol  and  alcohol  has  frequently  been  employed  as  a 
motor  fuel.     The  mixture  had  a  heat  value  of  14200  B.  t.  u.  per  Ib. 
Commercial  benzol  has  been  charged  with  excessive  carbon  formation, 
but  so  has  commercial  gasoline  of  the  present  day. 

There  seems  to  be  little  possibility  of  the  direct  use  of  crude  oil, 
coal  tar  (a  by-product  from  coal-gas  distillation)  or  tar  oil  (by-pro- 
duct from  tar  distillation)  in  the  cylinders  of  motor-car  engines. 
Even  in  stationary  engines  of  the  hot-cap  type  they  have  been  un- 


62  MOTOR  VEHICLES  AND  THEIR  ENGINES 

satisfactory.  Extremely  high  compression  and  still  higher  fuel- 
injection  pressures,  usually  complicated  by  an  air  blast,  have  thus  far 
been  necessary.  The  engines  have  been  heavy  and  costly  and  in 
many  instances  unreliable.  Kerosene  is  the  most  promising  cheaper 
fuel,  but  the  kerosene  problem  will  not  be  solved  until  the  starting 
problem,  as  well  as  the  running  problem,  is  solved.  There  seems  to 
be  no  good  ground  for  apprehension  that  the  substitution  of  kerosene 
will  leave  us  where  we  are  now,  as  far  as  cost  is  concerned.  The  yield 
of  kerosene  is  very  much  greater  than  that  of  high-grade  gasoline. 
In  fact,  kerosene  is  simply  low-grade  gasoline.  Circumstances  are 
compelling  the  use  of  lower  and  lower  grades,  so  that  a  gradual 
approximation  to  kerosene  as  fuel  seems  both  the  most  probable  and 
the  easiest  direction  for  progress.  The  necessary  modifications  of 
equipment  have  in  a  measure  been  already  anticipated  by  such 
devices  as  water-jacketed  and  hot-air-jacketed  carburetors,  etc. 


CHAPTER  VIII 


ELEMENTS  OF  CARBURETION 

Pure  gasoline  vapor  must  be  combined  with  oxygen  in  order  to 
render  it  inflammable.  The  simplest  manner  of  effecting  this  is  to 
mix  air  with  gasoline.  When  the  correct  proportions  are  obtained 
the  oxygen  supplied  by  the  air  will  be  sufficient  to  result  in  the  com- 
plete combustion  of  the  gasoline  vapor  without  a  surplus  of  either 
of  the  ingredients.  This  mixing  is  called  carburetion  and  the  air  is 
said  to  be  carbureted. 

The  carburetor  is  a  metering  device  whose  function  is  to  blend 
mechanically  a  liquid  fuel  with  a  certain  amount  of  air  to  produce 
as  nearly  a  homogeneous  mixture  as  possible  and  in  such  proportion 
as  will  result  in  as  perfect  an  explosive  mixture  as  can  be  obtained. 

With  a  liquid  fuel  such  as  gasoline  it  is  difficult  to  obtain  this 
perfect  mixture  especially  with  low  test  gasoline.  If  it  were  possible 
to  transform  a  liquid  fuel  into  its  vapor,  the  vapor  would  act  as  a 
gas  and  would  mix  easily  with  the  air  to  form  a  homogeneous  mixture. 
The  carburetor  should  be  so  designed  as  to  atomize  the  fuel  and  break 
it  up  into  as  small  particles  as  possible  so  every  minute  particle  of 
the  fuel  is  surrounded  by  the  correct  proportion  of  air  as  it  enters 
the  inlet  manifold  of  the  engine.  To  facilitate  the  vaporization  of 
these  minute  particles  of  fuel  it  is  advisable  to  heat  the  air  taken 
into  the  carburetor. 

There  is  a  range  of  proportions  of  air  to  vapor  for  a  given  fuel 
between  which  combustion  will  result.  This  range*  extends  from 
that  proportion  known  as  the  UPPER  LIMIT  OF  COMBUSTION 
to  that  known  as  the  LOWER  LIMIT  OF  COMBUSTION.  The 
upper  limit  is  reached  when  the  ratio  of  air  to  vapor  is  a  maximum 
at  which  combustion  will  take  place,  any  further  addition  in  air 
rendering  the  mixture  non-combustible.  The  lower  limit  is  reached 
when  the  ratio  of  air  to  vapor  is  a  minimum  at  which  combustion 
will  take  place,  any  decrease  in  air  below  this  point  producing  a  non- 
combustible  mixture.  It  should  be  remembered  that  the  limits  of 
combustion  are  dependent  upon  the  temperature  and  pressure. 

The  limits  of  combustion  of  gasoline  (70°  Sp.  Gr.)  can  be  taken 
approximately  as  follows:  Lower  limit,  7  parts  air  (by  weight)  to  1 
part  of  gasoline;  upper  limit,  20  parts  air  to  1  part  gasoline.  Under 
given  temperature  and  pressure  the  ratio  at  which  a  combustible 

63 


64  MOTOR  VEHICLES  AND  THEIR  ENGINES 

mixture  will  burn  depends  upon  the  ratio  of  air  to  vapor.  This  rate 
of  burning  is  known  as  the  RATE  OF  FLAME  PROPAGATION  and 
it  is  desirable  to  obtain  a  mixture  whose  rate  of  flame  propagation 
is  a  maximum  because  the  expansion  will  depend  upon  the  rapidity 
with  which  the  entire  mixture-  is  completely  burned. 

Rich  mixtures  have  a  greater  proportion  of  fuel  vapor  and  are 
slow  burning  and  sluggish.  They  also  cause  carbon  to  be  deposited 
in  the  combustion  space  because  of  their  incomplete  combustion. 
Mixtures  that  have  too  great  a  proportion  of  air  are  very  erratic  in 
their  combustion.  The  mixture  in  the  cylinders  is  often  formed  in 
layers  and  as  each  layer  burns  independently  of  the  other  the  rate  of 
burning  is  slow.  The  term  LEAN  MIXTURE  is  often  used  to  desig- 
nate not  only  this  type  of  mixture,  but  those  which  have  not  reached 
the  upper  limit.  These  mixtures  have  a  high  rate  of  flame  propa- 
gation. When  mixtures  are  too  lean  they  cause  misfiring  of  the 
engine  and  also  cause  back  firing  into  the  carburetor. 

A  carburetor  must  be  constructed  to  maintain  the  proper  pro- 
portions of  gasoline  and  air  under  all  conditions.  To  accomplish 
this  several  designs  and  principles  have  been  evolved  which  will  be 
discussed  in  the  following  chapters.  Types  of  carburetors  which 
are  not  commonly  used  will  not  be  discussed  because  the  principle 
upon  which  they  are  based  has  not  proven  satisfactory  for  motor 
vehicles. 

Before  taking  up  any  of  these  types  it  is  necessary  to  study  the 
basic  principles  underlying  carburetion.  These  will  be  most  clearly 
understood  when  applied  to  a  simple  carburetor  of  the  spray  nozzle 

type.  The  gasoline  supply  from 
the  storage  tank  enters  the  float 
chamber  "F"  of  the  carburetor 
and  as  the  gasoline  level  rises  the 
float  presses  against  the  levers  at 
the  top  of  the  float  chamber  (Fig. 
41).  These  levers  are  pivoted  so 
that  their  outer  ends  are  raised 
by  the  float.  Their  inner  ends 
working  in  a  collar  or  recess,  press 
the  float  needle  valve  downward 
into  its  seat.  This  shuts  off  the 

Fig.  41— Simple  Carburetor  suPP!y  of  gasoline  when  the  level 

in  the  float  chamber  has  reached 

the  proper  height.  The  height  at  which  this  gasoline  should  be  main-, 
tained  is  governed  by  the  nozzle  or  jet  "G."  The  level  must  stand 
approximately  %§  below  the  top  of  this  nozzle.  The  gasoline  is  fed 


ELEMENTS  OF  CARBURETION  65 

to  the  nozzle  "G"  from  the  float  chamber  through  the  pipe  "E." 
The  inlet  valve  being  open  when  the  piston  moves  outward  in  the 
cylinder  on  its  suction  stroke,  air  will  be  drawn  through  the  carburetor, 
as  indicated  by  the  arrows  in  Fig.  41,  passing  the  nozzle  on  its  way 
to  the  cylinders.  The  suction  created  by  the  rush  of  air  past  the 
spray  nozzle  causes  the  gasoline  to  be  delivered  to  the  mixing  chamber 
in  a  fine  spray.  Since  the  suction  depends  upon  the  velocity  of  the 
air  passing  the  nozzle,  a  Venturi  tube  "X"  is  used. 

A  Venturi  tube  is  a  tube  which  is  narrowed  at  the  center  so  that 
the  area  through  which  the  air  must  pass  is  considerably  decreased. 
As  the  same  amount  of  air  must  pass  through  every  point  in  the  tube 
its  velocity  will  be  greatest  at  the  narrowest  point.  The  more  this 
area  is  reduced  the  greater  will  be  the  velocity  of  the  air  and  the 
suction  will  be  proportionally  increased. 

The  sp^-ay  nozzle  should  be  located  where  the  suction  is  greatest 
which  is  just  above  the  narrowest  part  of  the  Venturi  tube.  The 
spray  of  gasoline  from  the  nozzle  and  the  air  entering  through  the 
Venturi  tube  are  mixed  together  in  the  mixing  chamber,  that  portion 
of  the  tube  immediately  above  the  spray  nozzle.  This  produces  a 
combustible  mixture  which  passes  through  the  intake  manifold  into 
the  cylinders. 

The  speed  of  the  engine  is  controlled  by  the  use  of  the  throttle 
"T"  which  is  a  form  of  damper  placed  between  the  mixing  chamber 
and  intake  manifold.  The  more  the  throttle  is  closed  the  greater 
will  be  the  obstacle  placed  in  this  passage  and  the  greater  will  be 
the  opposition  to  the  filling  of  the  cylinder  at  each  stroke.  This 
gives  a  less  powerful  impulse  to  the  piston  and  the  engine's  speed 
is  correspondingly  reduced. 

As  the  throttle  is  opened  the  speed  of  the  engine  increases  and 
with  wide  open  throttle  attains  its  maximum  speed  which  for  this 
discussion  will  be  assumed  to  be  1,600  revolutions  per  minute. 
The  cylinder  fills  as  freely  as  possible  and  a  large  quantity  of  air 
passes  through  the  carburetor  while  the  gasoline  jet  delivers  its 
maximum. 

As  the  load  on  the  engine  is  increased  as  will  be  the  case  when  a 
hill  is  encountered,  the  speed  is  gradually  diminished,  say  to  400 
R.  P.  M.  It  is  obvious  that  the  air  does  not  pass  through  the  car- 
buretor with  the  same  velocity  as  before  and  the  suction  is  greatly 
reduced,  although  the  throttle  is  still  wide  open.  It  is  evident  the 
throttle  does  not  wholly  control  the  speed  of  the  engine;  the  load  is 
also  a  factor  that  must  be  considered.  In  actual  test  with  wide  open 
throttle  the  engine  suction  has  decreased  over  nine  times  between 
1600  R.  P.  M.  and  400  R.  P.  M.  The  throttle  is  simply  a  means  to 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


prevent  the  engine  from  pulling  in  a  full  charge  of  mixture  each 
suction  stroke  and  thus  regulates  its  power. 

As  the  speed  of  the  engine  increases  the  suction  increases.  The 
flow  of  liquids  is  governed  by  definite  laws  and  the  flow  from  a  jet 
increases  under  suction  faster  than  the  corresponding  flow  of  air. 
With  a  simple  construction  of  nozzle  the  mixture  becomes  richer  as 
the  speed  increases.  As  it  is  essential  to  have  practically  the  same 
proportions  of  air  and  gasoline  at  all  speeds  it  is  necessary  to  construct 
the  carburetor  to  maintain  this  proportion  as  the  suction  increases. 

To  overcome  rich  mixtures  the  carburetor  must  be  adjustable  so 
that  less  gasoline  or  more  air  will  be  supplied.  The  gasoline  supply  is 
controlled  by  the  size  of  the  spray  nozzle  opening.  For  a  given 
suction  the  quantity  of  gasoline  delivered  varies  directly  as  the  cross 
sectional  area  at  the  nozzle.  In  some  carburetors  the  nozzle,  which 
is  of  fixed  size,  may  be  replaced  by  a  smaller  or  larger  nozzle  depending 
upon  the  regulation  desired. 


Fig.  42— Types  of  Needle  Valves 

In  other  carburetors  the  opening  at  the  nozzle  is  adjustable  by 
means  of  a  needle  valve  (Fig.  42).     As  the  needle  is  screwed  into  its 

seat  the  nozzle  area  is 
reduced  resulting  in  leaner 
mixtures. 

The  air  supply  may  be 
controlled  by  employing  an 
automatic  air  valve  (Fig. 
43).  This  consists  of  a 
valve  held  in  its  seat  by  a 
spring  whose  tension  is 
adjustable.  This  valve  is 
opened  automatically  by 
Fig.  43 — Auxiliary  Air  Carburetor  atmospheric  pressure  which 


ELEMENTS  OF  CARBURETION  67 

will  overcome  the  tension  of  the  spring  allowing  air  to  enter  the 
mixing  chamber.  As  the  tension  in  the  spring  is  increased  greater 
suction  will  be  required  to  open  the  valve  regulating  the  point  at 
which  the  valve  opens  and  the  amount  it  opens. 

The  auxiliary  air  entering  the  mixing  chamber  does  not  pass 
through  the  Venturi  tube  hence  it  dilutes  the  rich  mixture  resulting 
from  the  increased  suction.  In  this  manner  the  proportions  of  air 
and  gasoline  are  kept  constant  at  variable  speeds. 

PRECAUTIONS  WHEN  ADJUSTING  CARBURETOR.— Before 
attempting  to  put  a  carburetor  in  proper  adjustment  certain  con- 
ditions must  prevail. 

1.  The  engine  must  be  warm. 

2.  The    adjustment    must    be    made    under   actual   operating 
conditions. 

3.  There  must  be  no  leaks  allowing  air  which  does  not  pass 
through  the  carburetor  to  enter  the  combustion  space. 

4.  All  choking  devices  must  be  wide  open. 

5.  All  gasoline  passages  must  be  free  from  obstructions. 

6.  The  ignition  system  must  be  properly  timed  and  in  working 
order. 

In  making  carburetor  adjustments  it  is  desirable  to  obtain  as 
lean  a  mixture  as  will  give  proper  results.  Hence,  it  is  imperative 
first  to  diminish  the  proportions  of  gasoline  to  air  until  so  lean  a 
mixture  is  obtained  that  missing  of  the  engine  and  possibly  back 
firing  in  the  carburetor  results.  The  proportion  should  then  be 
gradually  increased  until  the  missing  is  overcome  and  the  engine 
runs  smoothly. 

When  making  any  changes  in  adjustment  it  is  necessary  that  only 
slight  changes  be  made  at  a  time.  After  every  change  of  adjustment 
sufficient  time  must  be  given  for  this  change  to  effect  the  operation 
of  the  engine  before  further  changes  are  made.  This  will  eliminate 
any  possibility  of  making  unnecessary  changes.  The  greatest  care 
must  be  observed  in  this  respect  when  overcoming  a  lean  mixture 
since  a  mixture  richer  than  necessary  may  result.  This  would  not 
be  noticed  in  the  running  of  the  engine  but  would  increase  the  fuel 
consumption  materially. 

Carbon  monoxide,  a  deadly  poisonous  gas,  is  present  in  the 
exhaust  of  gasoline  engines.  Increasing  the  proportion  of  gasoline 
to  air  in  the  mixture  increases  the  amount  of  carbon  monoxide  given 
off  at«  the  exhaust  pipe.  Because  of  the  presence  of  carbon  mon- 
oxide it  is  very  dangerous  to  run  the  engine  for  any  length  of  time 
while  the  car  is  in  a  small  closed  garage.  If  the  doors  and 
windows  are  open  the  danger  is  very  much  lessened,  but  it  is  far 


68  MOTOR  VEHICLES  AND  THEIR  ENGINES 

safer  if  an  adjustment  of  the  carburetor  is  being  made  to  run  the 
car  outside. 

Serious  personal  injury  may  be  caused  by  the  presence  of  carbon 
monoxide  in  a  garage  if  the  percentage  of  it  in  the  air  is  greater  than 
a  very  small  fraction  of  one  per  cent.  Unconsciousness  may  result 
without  warning.  It  is  reported  that  no  indication  of  danger  is 
given  by  personal  discomfort  until  too  late.  Deaths  resulting  from 
the  presence  of  carbon  monoxide  in  garages  have  been  reported. 

During  the  final  test  of  all  motor  apparatus  by  the  manufacturer 
the  carburetor  is  very  carefully  adjusted  and  this  adjustment  should 
not  be  changed  unless  it  is  absolutely  necessary  because  of  greatly 
changed  climatic  conditions  or  grade  of  fuel  used.  After  the  car- 
buretor is  adjusted  to  operate  under  these  conditions  there  should 
be  no  necessity  for  further  change. 

Engine  troubles  arise  from  many  sources  and  it  is  very  seldom 
that  the  trouble  is  due  to  the  carburetor  adjustment.  It  must  be 
borne  in  mind  that  a  properly  adjusted  carburetor  cannot  get  out  of 
adjustment  unless  tampered  with.  It  is  the  tendency  of  inexperi- 
enced men  to  adjust  the  carburetor  no  matter  what  the  trouble 
without  first  endeavoring  to  locate  the  real  difficulty.  This  leads  to 
the  adjusting  devices  becoming  worn  and  inaccurate.  Make  it  an 
inflexible  rule  to  try  to  locate  engine  troubles  at  all  other  possible 
sources  before  touching  the  carburetor. 

In  case  the  suction  through  the  carburetor  is  suddenly  increased 
by  quickly  opening  the  throttle,  the  air,  being  lighter  than  gasoline, 
will  respond  almost  instantly  and  its  flow  will  be  accelerated  very 
suddenly.  The  gasoline  particles  owing  to  that  characteristic  known 
as  "inertia,"  will  not  respond  so  rapidly  due  to  their  heavier  weight 
and  the  flow  of  gasoline  will  not  accelerate  as  rapidly  as  the  air. 
This  will  result  in  the  air  rushing  ahead  of  the  gasoline  particles  and 
the  proportion  of  air  to  gasoline  will  be  greater  until  the  inertia  has 
been  overcome  and  the  gasoline  particles  have  responded  completely 
to  the  increased  suction.  This  condition  will  take  place  unless  some 
provision  is  made  against  it.  That  is,  a  sudden  opening  of  the 
throttle  will  tend  to  produce  a  very  lean  mixture  at  the  engine  due 
to  the  lagging  of  the  gasoline.  A  lean  mixture  at  this  time,  when 
acceleration  is  desired,  will  be  detrimental.  It  is  at  this  particular 
time  that  additional  gasoline  is  most  desired  in  order  to  compensate 
for  this  lagging  and  maintain  the  proper  mixture  at  the  engine.  •  The 
device  which  accomplishes  this  result  is  known  as  an  "accelerating 
well."  The  construction  or  arrangement  of  this  device  will  be 
explained  as  each  type  of  carburetor  is  taken  up. 


ELEMENTS  OF  CARBURETION  69 

A  rich  mixture  is  required  when  starting  an  engine,  especially 
when  cold.  The  additional  gasoline  may  be  supplied  in  several  ways ; 
by  priming  through  the  priming  cocks,  by  " flooding"  the  carburetor, 
by  the  use  of  chokes,  or  by  a  dash  control  which  increases  the  gasoline 
supply  temporarily. 

The  practice  of  priming  should  not  be  resorted  to  unless  all  other 
methods  fail,  since  the  continued  addition  of  liquid  gasoline  to  the 
cylinders  cuts  the  lubricant,  causing  loss  of  compression  and  permits 
the  gasoline  to  run  past  the  pistons  into  the  crank  case.  The  result 
of  over-priming  makes  it  almost  impossible  to  start  the  engine  because 
of  the  abnormally  rich  mixture  obtained.  If  an  explosion  does  result 
the  power  will  not  be  sufficient  to  rotate  the  engine  until  another 
power  impulse  is  obtained. 

Pet  cocks  are  made  with  a  cup  which  will  hold  sufficient  gasoline 
for  proper  priming.  This  cup  should  be  filled,  the  cock  opened,  and 
again  closed.  The  common  practice  of  priming  without  regard  to 
the  amount  of  gasoline  used  generally  results  in  over-priming.  Before 
starting  an  engine  which  has  been  over-primed  the  pet  cocks  should 
be  opened  and  the  engine  cranked  until  the  piston  and  cylinder  walls 
have  been  lubricated.  Turning  the  engine  over  for  some  time  also 
frees  the  combustion  space  of  the  overrich  mixture.  This  must  be 
done  as  the  liquid  gasoline  adheres  to  the  piston  and  cylinder  walls 
enriching  each  incoming  charge. 

Flooding  the  carburetor  causes  the  float  chamber  to  be  filled  with 
gasoline  above  the  level  at  which  it  ordinarily  stands.  Gasoline 
will  overflow  from  the  spray  nozzle  by  gravity  and  be  picked  up  by 
the  primary  air  and  carried  into  the  cylinders. 

Rich  mixtures  for  starting  may  also  be  obtained  by  the  use  of 
chokes.  These  are  placed  in  the  air  passages  making  it  difficult  to 
draw  air,  the  suction  being  satisfied  by  an  increased  amount  of 
gasoline  vapor.  Choking  devices  are  provided  on  some  carburetors 
to  cut  down  the  supply  of  air  until  the  engine  is  heated. 

All  liquids  vaporize  when  heated  sufficiently  and  while  gaso- 
line will  vaporize  at  ordinary  temperatures,  increased  heat  improves 
this  vaporization.  This  tends  to  reduce  the  percentage  of  liquid 
gasoline  in  the  mixing  chamber  causing  a  more  intimate  combina* 
tion  of  the  air  and  gas.  This  heat  may  be  obtained  several  ways; 
by  passing  air  heated  by  the  cylinder  or  exhaust  pipe  through 
the  carburetor,  by  water  jacketing  the  mixing  chamber  of  the  car- 
buretor, by  water  jacketing  the  inlet  manifold,  or  by  combining  the 
inlet  and  exhaust  manifolds  so  that  the  exhaust  gases  heat  the 
incoming  charge. 


70 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


There  are  two  common  types  of  float  chambers;  the  concentric 
in  which  the  float  chamber  is  placed  around  the  Venturi  tube  and  is 
concentric  with  it,  the  eccentric  in  which  the  float  chamber  is  placed 
by  the  side  of  the  Venturi  tube. 


Fig.  44 — Effect  of  Grades  on  Eccentric  Type  Carburetor 


Fig.  44  shows  an  eccentric  type  float  chamber  and  the  normal 
gasoline  level  is  shown  by  the  line  in  "A."  When  the  carburetor  is 
tilted  due  to  the  car  ascending  or  descending  a  grade  the  level  will  be 
changed  as  shown  in  "B  "  or  "C."  This  causes  too  much  or  too  little 

gasoline  to  be  supplied  by  the 
nozzle  giving  imperfect  mixtures. 
To  prevent  lean  mixtures  when 
ascending  grades  a  carburetor 
with  this  type  of  float  chamber 
should  be  attached  with  the 
float  chamber  towards  the 
radiator.  This  difficulty  will 
not  be  experienced  with  a 
concentric  float  type  of  car- 
buretor. The  level  at  the 
nozzle  always  remains  constant 
as  shown  in  Fig.  45  by  the 


Fig.  45— Effect  of  Grades  on 
Concentric  Type  Carburetor 


different  levels  A-A,  B-B,  and 
C-C.      This   accounts  for  the 
usage  of  concentric  float  car- 
buretors on  motor  cycles,  tractors,  or  other  motor  vehicles  which  are 
not  designed  for  the  ordinary  road  work. 


ELEMENTS  OF  CARBURETION  71 

GOVERNORS. — In  order  to  automatically  limit  both  the  vehicle 
and  engine  speed  at  all  times,  a  governor  is  provided.  It  consists 
of  a  grid  or  butterfly  valve  in  the  inlet  manifold  controlled  by  the 
action  of  movable  weights  attached  by  levers  to  the  driven  shaft  and 
valve  mechanism.  Centrifugal  force  which  results  from  whirling 
the  weights  around  the  shaft  causes  them  to  pull  away.  This  action 
moves  the  valve  in  the  intake  manifold  cutting  down  the  supply 
of  gas. 

The  position  of  these  weights  will  depend  upon  the  speed  of  the 
engine  and  at  approximately  1200  R.  P.  M.  the  gas  supply  will  be 
cut  off,  restricting  the  engine  and  consequently  the  vehicle  speed. 
This  governing  limits  the  speed  of  the  machine  to  about  15  miles 
per  hour. 

The  drive  is  thru  a  flexible  shaft.  It  is  driven  by  a  set  of  gears 
from  the  cam  shaft  or  by  the  fly  wheel.  An  adjustment  is  provided 
for  varying  the  setting  of  the  governor. 


CHAPTER  IX 


CARBURETORS 

The  operation  and  adjustment  of  the  various  types  of  carburetors 
most  commonly  used  will  be  outlined  giving  the  particular  points 
in  which  they  vary. 

SCHEBLER— MODEL  "E" 

This  carburetor  is  a  concentric  float  auxiliary  air  type  and  is  a 
very  simple  carburetor.  The  primary  air  inlet  is  through  an  air 
bend  at  the  bottom  of  the  carburetor  passing  the  spray  nozzle  and 
the  auxiliary  air  inlet,  controlled  by  the  usual  type  of  valve,  is  pro- 
vided at  the  top  of  the  mixing  chamber.  The  spray  nozzle  is  regu- 
lated by  the  needle  valve  (Fig.  46). 


Air  Valve  Sprl< 
Leather  Air  Value  Dk 


Auxiliary  Air  Port 
Throttle  Levef 

Throttle  Disc 
Oas  Outlet 


Lock  Spring 
Loch  Nut 

Air  Value  Adjusting 
Sere  iv 


Primary  Air  Inlet 
Air  Bend 


Float  Valve 

'nlon  Nut 
Union  Nipple 

\ 

Reversible  Union  Ell 


Needle  Valve  Packing  Nut 
Gasoline  AdjustingNeedle  Value 


Fig.  46— Sehebler  Model  E 

72 


CARBURETORS  73 

LOW  SPEED  ADJUSTMENT.— Have  the  auxiliary  air  valve 
spring  tension  tight,  then  adjust  by  the  needle  valve  turning  to  the 
right  until  the  mixture  is  too  lean,  and  then  turn  gradually  to  the 
left  until  the  missing  of  the  engine  is  eliminated  and  the  engine  runs 
smoothly. 

HIGH  SPEED  ADJUSTMENT.— Release  the  tension  on  the 
auxiliary  air  valve  spring  until  so  much  air  is  supplied  that  missing 
of  the  engine  results  and  then  tighten  the  spring  tension  until  the 
engine  runs  smoothly.  With  these  settings  the  increasingly  rich 
mixture  of  the  primary  should  be  compensated  for  by  the  extra 
auxiliary  air  at  all  speeds. 

THE  SCHEBLER— MODEL  "H" 

This  carburetor  is  for  motor-cycle  use  and  is  of  the  auxiliary  air 
type  having  a  "lift  needle  valve."  The  supply  of  gasoline  is  con- 
trolled by  a  needle  "E"  and  cam  adjustment,  which  insures  the 
proper  amount  of  gasoline  at  all  speeds.  As  the  throttle  is  opened 
the  needle  rises  from  its  seat. 

An  air  elbow  is  attached  to  the  primary  air  passage  of  the  car- 
buretor so  that  it  can  be  turned  to  any  convenient  angle  in  order  to 
draw  warm  air  off  the  cylinders  (Fig.  47). 

LOW  SPEED  ADJUSTMENT.— See  that  the  leather  air  valve 
"A"  seats  lightly  and  then  turn  knurled  button  "I"  to  the  right  until 
the  needle  "E"  seats  in  the  spray  nozzle  cutting  off  the  flow  of  gasoline. 
Now  turn  "I"  to  the  left  about  three  turns  and  open  low  speed  air 
adjusting  screw  "L"  about  three  turns  and  then  open  throttle  about 
half  way  to  start  the  engine.  After  starting  the  engine  close  the 
throttle  and  turn  needle  valve  adjusting  screw  "I"  to  the  right  until 
the  mixture  becomes  so  lean  that  the  engine  back  fires  or  misses. 
Then  turn  adjusting  nut  "I"  to  the  left  slowly,  notch  by  notch,  until 
the  engine  runs  smoothly.  If,  with  this  low  speed  adjustment,  the 
engine  runs  too  fast  turn  low  speed  adjusting  screw  "L"  to  the  right 
thus  ^increasing  the  size  of  the  throttle  opening. 

HIGH  SPEED  ADJUSTMENT.— The  carburetor  is  now  ready 
for  high  speed  adjustment  and  the  throttle  should  be  opened  and  the 
spark  advanced.  The  machine  should  be  run  at  high  speed  on  the 
road.  The  adjustment  is  now  made  by  the  pointer  "Z"  which,  as 
it  moves  from  "1"  toward  "3,"  increases  the  supply  of  gas  as  it 
allows  the  needle  valve  "E"  to  be  raised  higher  out  of  the  nozzle. 
Moving  the  indicator  "Z"  from  "3"  towards  "1"  cuts  down  the 
supply  of  gasoline  as  it  raises  the  cam  and  does  not  allow  the  needle 
to  move  as  far  out  of  the  nozzle.  When  the  indicator  reaches  the 


74 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


correct  point  the  engine  will  run  without  missing  or  back  firing.  If, 
when  lever  "  Z"  is  turned  to  "3  "  the  mixture  is  still  too  lean,  causing 
the  engine  to  miss  and  back  fire,  increase  the  tension  of  auxiliary 
air  valve  spring  by  turning  adjusting  screw  "12"  to  the  left. 


Fig.  47—Schebler  Model  H 

The  air  lever  on  the  side  of  the  mixing  chamber  should  be  opened 
when  extremely  high  speed  is  desired.  Be  sure  to  shut  this  port 
before  the  engine  is  stopped  because  difficulty  will  be  experienced  in 
starting  if  this  port  is  left  open. 

STARTING.— To  facilitate  easy  starting  of  the  engine  pull  out 
the  knurled  button  "12"  and  turn  to  the  right  or  left  so  that  it 
cannot  fall  back  in  the  recess.  This  tightens  the  spring  on  the 
auxiliary  air  valve  preventing  a  large  quantity  of  cold  air  rushing 
past  this  valve.  The  cold  air  admitted  to  the  carburetor  will  come 
only  through  the  primary  air  passage  past  the  nozzle  insuring  a  rich 
mixture  which  will  facilitate  easy  starting. 

After  the  engine  starts  the  knurled  button  "12"  should  be  turned 
back  to  release  the  spring  tension.  Just  after  the  engine  starts  it 


CARBURETORS 


75 


will  often  be  inclined  to  back  fire  which  is  caused  by  the  parts  being 
cold.  In  this  case  the  knurled  button  "12"  should  be  dropped  into 
recess  marked  "2"  until  the  engine  warms  up. 

KINGSTON— MODEL  "E" 

This  is  an  auxiliary  air  type  of  carburetor  with  concentric  float 
chamber.     The  construction  is  shown  in  Fig.  48. 


Fig.  48 — Kingston  Model  E 


The  principle  involved,  while  simple,  requires  some  explanation. 
Gasoline  is  admitted  at  connection  "24"  and  continues  to  flow  until 
valve  "22"  is  seated  due  to  the  proper  height  of  gasoline  being 
obtained.  From  the  float  chamber  the  gasoline  passes  to  the  spray 
nozzle  the  shape  of  which  should  be  particularly  noticed  as  it  forms 
a  cup  around  the  needle  valve  above  its  seat,  the  level  being  1/32//  below 
the  top  of  the  cup. 

When  starting  this  excess  of  gasoline  is  drawn  up  with  the  primary 
air  and  furnishes  a  very  rich  mixture.  As  the  speed  increases  this 
cup  is  emptied,  the  supply  being  drawn  from  and  regulated  by  the 
adjustment  of  needle  valve  "7"  at  its  seat. 

Both  primary  and  auxiliary  air  are  drawn  from  a  common  source 
passing  controller  or  choke  "11."  The  primary  air  passes  down  the 
primary  air  passage  "3"  and  up  through  the  Venturi  tube. 

The  auxiliary  air  in  this  carburetor  is  not  controlled  by  a  valve 
but  by  five  balls  "2"  which  are  lifted  from  their  seats  by  suction. 
These  balls  are  seated  at  different  depths  and  as  the  suction  increases, 
they  permit  a  greater  amount  of  air  to  pass  by  them.  There  is  no 
adjustment,  their  action  being  automatic  and  arranged  by  the 
manufacturer* 


76  MOTOR  VEHICLES  AND  THEIR  ENGINES 

The  only  adjustment  on  this  carburetor  is  the  needle  valve  which 
should  be  set  to  give  the  proper  results  at  the  speed  which  the  ap- 
paratus will  be  habitually  used.  The  needle  valve  when  turned  to 
the  right,  gives  leaner  mixtures  and  when  turned  to  the  left  gives 
richer  mixtures.  The  action  of  the  auxiliary  air  should  compensate 
for  any  change  in  speed. 

PACKARD 

This  carburetor  is  of  the  auxiliary  air  type  with  eccentric  float 
chamber.  The  gasoline  flows  into  the  float  chamber  through  a 
needle  valve  and  then  into  the  nozzle  "40"  (Fig.  49). 

The  mixing  chamber  is  surrounded  by  a  water  jacket  through 
which  passes  warm  water  taken  from  the  water  circulation  system. 
This  maintains  a  uniform  temperature  and  insures  efficiency  in  mixing 
the  sprayed  gasoline  with  air.  The  air  has  two  paths  through  which 
it  can  enter  the  carburetor,  the  primary  air  inlet  "33"  and  the 
auxiliary  air  inlet  "26."  The  primary  air  in  passing  the  nozzle  picks 
up  the  gasoline.  The  auxiliary  air  does  not  pass  the  nozzle  and  there- 
fore enters  the  mixing  chamber  as  pure  air. 

It  is  important  that  the  mixture  of  air  and  gasoline  be  kept  at  a 
constant  proportion.  Although  the  primary  air  inlet  valve  is  large 
enough  to  supply  air  for  all  conditions,  the  proportion  of  air  and  gas 
does  not  remain  constant  as  the  suction  increases,  therefore  auxiliary 
air  is  necessary.  The  auxiliary  air  inlet  valve  is  controlled  by  springs 
so  that  while  the  valve  opens  slightly  at  low  speed  the  increased 
suction  at  high  speed  opens  it  still  more,  admitting  a  greater  amount 
of  air,  thus  compensating  for  the  rich  mixture  through  the  primary. 

The  primary  air  intake  is  from  around  the  outside  of  the  exhaust 
pipe.  This  provides  a  supply  of  warm  air  which  prevents  condensa- 
tion in  the  carburetor  and  in  cold  weather  materially  assists  in  the 
vaporization  of  the  gasoline.  There  is  a  regulator  "30"  so  that  the 
proportion  of  warm  and  cold  air  may  be  regulated. 

AUXILIARY  AIR  VALVE.— The  valve  is  controlled  by  the  tension 
of  two  springs  one  within  the  other.  The  tension  of  the  springs  is 
regulated  by  a  wedge  underneath  them.  This  wedge  is  connected 
to  the  control  board  and  when  it  is  moved  towards  the  word  "gas" 
the  tension  of  the  springs  is  increased  causing  richer  mixtures. 
This  assists  in  starting  especially  in  cold  weather  and  the  lever 
should  be  kept  more  to  the  side  "gas"  than  "air"  until  the  engine 
warms  up.  This  is  the  only  regulation  on  this  carburetor. 

To  further  facilitate  starting  in  cold  weather  there  are  chokes  in 
both  primary  and  auxiliary  air  intakes. 


Si/..  i 


77 


78 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


PEERLESS 

This  carburetor  is  of  the  auxiliary  air  type  with  eccentric  float 
chamber  (Fig.  59).  The  gasoline  enters  the  float  chamber  passing 
through  the  screen  "1107."  The  level  at  which  the  gasoline  is 
maintained  in  the  float  chamber  is  controlled  by  the  float  "1100" 
which  operates  the  levers  "1096"  which  in  turn  operate  the  needle 
valve  "1101."  From  the  float  chamber  the  gasoline  passes  directly 
to  the  nozzle  "1110"  which  supplies  gasoline  to  the  mixing  chamber. 


Fig.  50 — Peerless  Carburetor 

Air  enters  the  mixing  chamber  from  two  sources:  the  primary 
air  entering  at  the  primary  air  intake,  passing  the  nozzle  located  at 
the  center  of  the  Venturi  tube  "1112,"  picking  up  gasoline  from  the 
spray  nozzle;  the  auxiliary  air  enters  at  the  automatic  air  intake 
valve  "  1079  "  which  is  held  in  its  seat  by  spring  "  1081."  The  auxili- 


CARBURETORS  79 

ary  air  enters  the  mixing  chamber  as  pure  air  compensating  for  the 
rich  mixture  from  the  primary  at  high  speed. 

The  mixing  chamber  is  water  jacketed  which  assists  materially 
in  vaporizing  the  gasoline  and  producing  a  more  nearly  homogeneous 
mixture. 

The  throttle  is  not  of  the  usual  butterfly  construction,  but  con- 
sists of  a  valve  having  two  seats.  Before  leaving  the  factory  the 
seat  "1065"  is  so  adjusted  that  it  will  allow  the  proper  amount  of 
mixture  to  enter  the  cylinders  when  idling.  The  throttle  "1064" 
is  controlled  by  the  throttle  lever  at  the  top  of  the  steering  column 
or  by  the  accelerator  pedal. 

To  adjust  this  carburetor  the  tension  on  the  auxiliary  air  valve 
spring  is  changed.  When  nut  "1085"  is  turned  to  the  right,  it 
increases  the  tension  on  the  spring,  thus  reducing  the  amount  of 
auxiliary  air  entering  the  mixing  chamber  for  a  given  amount  of 
suction  causing  the  mixtures  to  become  richer.  When  nut  "1085" 
is  turned  to  the  left  it  weakens  the  tension  on  the  spring,  thus  causes 
leaner  mixtures. 

To  limit  the  maximum  amount  that  the  auxiliary  air  valve  can 
open,  an  adjusting  nut  "1086"  is  placed  on  the  lower  side  of  the 
auxiliary  air  valve.  By  turning  this  to  the  left  it  will  limit  the 
maximum  amount  that  the  valve  can  open,  thereby  reducing  the 
amount  of  air  which  enters  at  high  speed.  This  adjustment  should 
be  made  so  that  it  does  not  effect  the  operation  at  any  point  except 
extremely  high  speed. 

FIERCE-ARROW 

This  carburetor  (Fig.  51)  is  of  the  auxiliary  air  type  with  eccentric 
float  chamber.  Gasoline  enters  the  float  chamber  from  the  tank, 
the  level  being  controlled  in  the  usual  way.  Valve  "P"  is  operated 
by  levers  "M"  which  in  turn  are  operated  by  the  float.  From  the 
float  chamber  gasoline  passes  direct  to  the  nozzle  "A-I."  The 
primary  air  enters  through  the  tube  "K-l,"  passing  through  the 
small  Venturi  tube  "L-l,"  picking  up  gasoline  from  the  nozzle,  and 
carrying  it  to  mixing  chamber  "L."  The  auxiliary  air  is  admitted 
through  the  carefully  calibrated  reed  valves  "Q-l"  and  "N-l." 
There  is  no  method  of  regulating  auxiliary  air.  The  only  regulation 
on  this  carburetor  affecting  the  mixture  is  by  the  needle  valve  "D-l." 
When  screwed  to  the  right  it  will  give  leaner  mixtures  and  when 
screwed  to  the  left  it  will  give  richer  mixtures. 

This  carburetor  is  equipped  with  an  adjustment  for  regulating 
the  temperature  of  the  air  passing  through  the  primary  air  inlet. 


80 


CARBURETORS 


81 


Cold  air  regulator  "I"  is  located  at  the  rear  of  the  carburetor;  in 
warm  weather  the  pointer  of  the  regulator  should  be  set  to  read 
"open,"  in  cold  weather  it  should  be  set  to  read  "closed."  Any 
intermediate  adjustments  can  be  made  according  to  the  temperature. 
There  is  also  a  hot  water  jacket  "T-l"  around  the  mixing  chamber. 
It  is  connected  by  pipe  "D"  from  the  carburetor  to  the  outlet  water 
pipe  and  is  equipped  with  a  cock.  In  warm  weather  this  may  be 
closed  partially  or  entirely.  By  the  use  of  these  two  adjustments 
incorrect  mixtures  encountered  because  of  the  lower  grades  of  gasoline 
can  be  overcome  as  vaporization  depends  upon  temperature. 


STROMBERG— MODEL  "G" 

This  is  an  auxiliary  air  type  of  carburetor  with  eccentric  float 
chamber.  The  gasoline  enters  the  float  chamber  and  passes  to  the 
two  nozzles  "C"  and  "J." 


Fig.  52 — Stromberg  Model  G 

When  the  engine  is  idling^ir  is  drawn  through  the  primary  intake 
passes  around  the  primary  nozzle  "C"  from  which  a  jet  of  gasoline  is 
spraying.  Under  load  the  air  valve  "E"  allows  additional  air  to  be 
sucked  in  past  the  auxiliary  nozzle  "J,"  producing  a  mixture  which 


82  MOTOR  VEHICLES  AND  THEIR  ENGINES 

unites  with  the  primary  mixture  formed  in  the  Venturi  tube  and 
passes  by  the  throttle  valve  to  the  inlet  manifold. 

There  are  only  two  simple  adjustments  that  ever  need  attention, 
"A"  the  low  speed  adjusting  nut  and  "B"  the  high  speed  adjusting 
nut  (Fig.  52).  To  adjust  this  carburetor  precede  as  follows: 
With  the  engine  at  rest  set  the  high  speed  nut  "B"  so  there  is  at 
least  Vie  of  an  inch  clearance  between  the  spring  "G"  and  the  nut 
"X"  above  it.  This  is  imperative.  Set  the  low  speed  nut  "A"  so 
the  air  valve  "E"  is  seated  lightly. 

Start  the  engine,  first  closing  the  choke  valve  "R"  in  the  air  horn 
by  the  control  provided.  Open  this  as  soon  as  the  engine  starts  and 
keep  open  while  engine  is  running.  If  engine  does  not  start  on  the 
third  or  fourth  turn  of  the  crank  open  this  valve  and  engine  should 
then  run. 

LOW  SPEED. — Do  not  adjust  carburetor  until  engine  is  thor- 
oughly warmed  up.  When  engine  is  warm  and  with  spark  retarded, 
adjust  nut  "  A"  up  or  down  until  engine  runs  smoothly  at  low  speed. 
To  determine  proper  adjustment  open  the  air  valve  with  finger  by 
depressing  "X"  slightly.  If  this  causes  the  engine  to  speed  up 
noticeably  it  indicates  too  rich  a  mixture  and  "A"  should  be  turned 
down  notch  by  notch.  If  this  causes  the  engine  to  die  suddenly 
when  slightly  opening  the  air  valve  it  indicates  too  lean  a  mixture, 
and  "A"  should  be  turned  up  until  this  is  overcome.  Once  properly 
set  for  idling  do  not  change  this  adjustment  when  making  the  high 
speed  adjustment. 

HIGH  SPEED. — Advance  the  spark  to  the  normal  position  and 
open  the  throttle  gradually.  If  engine  back  fires  through  the  car- 
buretor it  is  a  positive  indication  of  too  lean  a  mixture  and  nut  "B" 
should  be  turned  up  notch  by  notch  until  this  is  overcome. 

If  mixture  is  too  rich  as  indicated  by  " galloping"  of  the  engine 
and  heavy  black  smoke  from  the  exhaust,  turn  "B"  down  until  engine 
operates  properly.  A  further  test  for  the  correct  mixture  at  high 
speed  can  be  made  by  depressing  the  air  valve  when  the  engine  is 
running  at  this  speed.  If  engine  speeds  up  it  indicates  too  rich  a 
mixture,  if  engine  runs  slower  too  lean  a  mixture. 

Turning  either  adjusting  nut  up  means  a  richer  mixture  or  more 
gasoline;  down  means  a  leaner  mixture  or  more  air. 

TO  FIND  PROPER  NOZZLE  SIZE.— Carburetors  are  equipped 
with  the  proper  size  nozzle  before  leaving  the  factory  and  on  changes 
should  be  made  unless  absolutely  necessary.  Before  changing 
examine  all  manifold  and  valve  head  connections  for  air  leaks.  It 
is  absolutely  impossible  to  make  the  carburetor  operate  properly  if 
there  are  any  air  leaks  in  the  engine. 


CARBURETORS  83 

DOUBLE  JET  TYPE.— If  after  following  the  instructions  given 
for  adjustment  with  the  engine  running  idle  at  low  speed  the  air 
valve  "E"  remains  tightly  seated  it  indicates  too  small  a  primary 
nozzle  "C"  and  a  larger  one  should  be  substituted. 

If  with  the  proper  adjustment  and  after  stopping  the  engine  the 
air  valve  "E"  hangs  off  the  seat  the  primary  nozzle  is  too  large  and 
a  smaller  one  should  be  used. 

To  change  primary  nozzle  remove  pet  cock  or  plug  at  "P,"  insert 
screwdriver,  and  unscrew  nozzle. 

If  the  mixture  on  low  speed  is  correct  but  to  get  the  proper  high 
speed  adjustment  it  is  necessary  to  turn  nut  "B"  up  so  far  that  the 
spring  "G"  is  in  contact  with  "X"  above  it,  after  the  engine  is  shut 
down,  it  indicates  that  the  auxiliary  nozzle  "J"  is  too  small  and  a 
larger  one  should  be  used. 

If  the  mixture  on  high  speed  is  correct  but  to  get  the  proper 
adjustment  it  is  necessary  to  turn  nut  "B"  down  so  that  there  is 
more  than  y%  of  an  inch  clearance  between  "G"  and  "X,"  when 
the  engine  is  shut  down,  it  indicates  too  large  an  auxiliary  nozzle 
"J"  and  a  smaller  one  should  be  used. 

To  change  auxiliary  nozzle  "  J"  move  air  horn  to  one  side,  remove 
plug  "A-P,"  insert  screwdriver,  and  unscrew  "J."  Nozzles  are 
numbered  according  to  drill  gauge  sizes;  for  instance,  -No.  59  is 
larger  than  No.  60. 

SEASON  ADJUSTMENT.— Open  shutter  "T"  in  summer, 
close  in  winter.  To  get  best  results  from  this  carburetor  warm  air 
should  be  supplied  to  the  hot  air  horn  of  the  carburetor  from  around 
the  exhaust  manifold. 

CADILLAC 

This  is  an  auxiliary  air  type  carburetor  with  concentric  float 
chamber.  The  gasoline  enters  the  float  chamber  through  the  gasoline 
inlet  passage  passing  the  gasoline  inlet  needle  valve.  The  air  is 
supplied  from  two  sources;  the  primary  air  enters  at  the  primary 
air  inlet  passing  the  nozzle  at  the  Venturi  tube,  the  secondary  air 
enters  at  the  auxiliary  air  valve  entering  the  mixing  chamber  as 
pure  air. 

A  leaning  device,  sometimes  called  a  "gas-saver,"  is  provided 
which  may  be  adjusted  to  cause  a  mixture  in  which  the  proportion 
of  gasoline  to  air  is  cut  down  for  ordinary  driving  speeds.  The 
mixture  is  not  affected  by  the  leaning  device  at  the  closed  or  nearly 
closed  position  of  the  throttle,  or  at  the  open  or  nearly  open  position. 
The  leaning  device  is  adjusted  at  "  G  "  (Fig.  53) .  When  the  adjusting 


84 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


Cadillac  Carburetor 


AUTOMATIC  THROTTLE 

THROTTLE 
'AUXILIARY  AIR  VAtvt 


•I 


FLOA 

CATCH  BASIN 
DRAIN   PIPE 


GASOLINE  INLET 
PASSAGE 


GASOLINf  INLEl 
NEEDLE  VALVE 


-THKOTTtE  PUMP 


!H- DRAIN  PIPE 


Fig.  53 — Cross-Section  of  Cadillac  Carburetor 


CARBURETORS  85 

screw  "G"  is  screwed  in  as  far  as  it  will  go  the  leaning  device  has  no 
influence  on  the  mixture  at  any  throttle  position. 

The  leaning  device  consists  of  a  shutter  attached  to  the  right 
hand  end  of  the  throttle  shaft  which  covers  a  slot  in  the  carburetor 
body  when  the  throttle  is  opened  slightly  and  then  uncovers  the  slot 
when  the  throttle  is  opened  wide  or  nearly  so.  A  hole  is  drilled 
through  the  carburetor  body  from  the  mixing  chamber  to  the  slot 
and  another  hole  is  drilled  from  the  float  chamber  to  the  slot.  When 
the  slot  is  covered  by  the  shutter,  a  passage  is  formed  from  the  mixing 
chamber  to  the  float  chamber.  The  partial  vacuum  in  the  mixing 
chamber  causes  a  lowering  of  the  air  pressure  in  the  float  chamber 
resulting  in  less  gasoline  being  fed  through  the  spray  nozzle.  When 
the  shutter  uncovers  the  slot  the  partial  vacuum  in  the  mixing 
chamber  has  no  effect  on  the  air  pressure  in  the  float  chamber  and 
the  amount  of  gasoline  fed  through  the  spray  nozzle  is  not  affected. 

This  carburetor  is  equipped  with  a  device  to  force  gasoline 
through  the  spraying  nozzle  when  the  throttle  is  opened  quickly  for 
acceleration  and  is  called  the  "throttle  pump."  It  is  so  arranged 
that  when  opening  the  throttle  slowly  it  will  have  no  effect  on  the 
mixture  but  when  sudden  acceleration  is  desired  the  plunger  will  be 
forced  down  suddenly  as  the  throttle  is  opened.  In  this  way  the 
gasoline  is  forced  out  of  the  spray  nozzle.  As  the  throttle  is  closed 
the  chamber  below  the  plunger  fills  up. 

The  carburetor  is  equipped  with  an  automatic  throttle  (Fig.  53) 
controlled  by  a  spring.  Its  purpose  is  to  prevent  pulsations  of  air 
in  the  intake  manifold  from  causing  the  auxiliary  air  valve  to  flutter 
when  the  engine  is  running  slowly  with  the  throttle  fully  opened. 
The  automatic  throttle  is  adjusted  when  the  carburetor  is  assembled 
and  requires  no  further  attention. 

METHOD  OF  ADJUSTMENT.— Move  the  spark  lever  to  the 
extreme  left  to  retard  the  spark  on  the  sector  and  the  throttle  lever 
to  a  position  which  leaves  the  throttle  in  the  carburetor  slightly 
open.  Adjust  the  air  valve  screw  "A"  to  a  point  which  produces 
the  highest  engine  speed.  Turning  the  screw  "A"  in  a  clockwise 
direction  increases  the  proportion  of  gasoline  to  air  in  the  mixture 
and  vice  versa. 

Close  the  throttle  (move  it  to  the  extreme  left  on  the  sector)  and 
adjust  the  throttle  stop  screw  "B"  to  a  point  which  causes  the  engine 
to  run  at  a  speed  of  about  300  revolutions  per  minute.  The  spark 
lever  should  be  at  the  extreme  left  on  the  sector  when  this  adjustment 
is  made. 

With  the  spark  and  throttle  levers  at  the  extreme  left  on  the 
sector  adjust  the  air  valve  screw  "A"  to  a  point  which  produces  the 


86  MOTOR  VEHICLES  AND  THEIR  ENGINES 

highest  engine  speed.  Open  the  throttle  until  the  shutter  attached 
to  the  right  hand  end  of  the  throttle  shaft  just  covers  the  slot  in  the 
carburetor  body.  Then  adjust  the  screw  "  G  "  to  a  point  which  pro- 
duces the  highest  engine  speed  or  to  a  point  where  the  engine  misses 
from  too  lean  a  mixture,  then  overcome  the  missing  by  turning  the 
screw  "G"  in  a  clockwise  direction  increasing  the  proportion  of  gaso- 
line to  air  in  the  mixture. 

During  very  cold  weather  when  a  slightly  richer  mixture  is  de- 
sirable it  may  be  found  best  to  turn  the  adjusting  screw  "G"  further 
in  a  clockwise  direction. 

SETTING  OF  CARBURETOR  FLOAT.— After  the  carburetor 
has  been  in  use  for  sometime  there  may  be  a  slight  amount  of  wear 
at  the  point  of  the  inlet  needle  and  its  seat.  If  this  should  occur 
the  height  of  the  gasoline  in  the  carburetor  bowl  will  rise. 

To  determine  if  the  float  is  properly  set  remove  the  carburetor 
from  the  engine  and  the  bowl  from  the  carburetor.  Raise  the  float 
until  the  inlet  needle  valve  is  just  closed.  The  dimension  "A" 
(Fig.  53)  should  then  be  one-half  inch.  The  setting  may  be  corrected 
by  slightly  bending  the  arm  to  which  the  float  is  attached. 

MARVEL 

This  is  an  auxiliary  air  type  of  carburetor  with  eccentric  float 
chamber.  The  spray  nozzle  opening  is  regulated  by  a  needle  valve 
which  constitutes  the  gasoline  adjustment  of  the  carburetor  and  it 
is  surrounded  by  the  Venturi  tube,  through  which  a  portion  of  the 
incoming  air  passes  at  high  velocity,  picking  up  gasoline  from  the 
end  of  the  spray  nozzle. 

The  mixing  chamber  also  contains  the  air  valve  and  the  high 
speed  nozzle.  The  auxiliary  air  valve  is  held  to  its  seat  by  an  adjust- 
able spring  which  forms  the  air  adjustment.  At  a  high  rate  of  speed 
the  suction  increases.  This  causes  the  auxiliary  air  valve  to  lift 
from  its  seat  admitting  additional  air  mixed  with  gasoline  drawn 
from  the  high  speed  nozzle  (Fig.  54). 

The  air  enters  the  carburetor  through  a  three-way  valve  connected 
to  the  air  regulator  on  the  instrument  board.  By  means  of  this  valve 
the  air  can  be  taken  from  the  heater  under  the  exhaust  manifold  or 
directly  from  the  atmosphere.  In  the  " choke"  position  this  valve 
partly  closes  the  air  intake  causing  the  engine  to  draw  excessively 
rich  charges  for  starting. 

The  opening  between  the  mixing  chamber  and  the  intake  manifold 
is  controlled  by  a  butterfly  valve.  This  is  connected  to  the  throttle 
lever  on  the  steering  wheel  and  thus  regulates  the  amount  of  mixture 
being  fed  to  the  engine. 


87 


88  MOTOR  VEHICLES  AND  THEIR  ENGINES 

The  upper  end  of  the  mixing  chamber  and  the  Venturi  tube  are 
surrounded  by  jackets  through  which  some  of  the  hot  exhaust  gas 
passes  to  keep  the  carburetor  warm  and  assist  vaporization  of  the 
fuel.  A  damper  in  the  jacket  opening  is  connected  to  and  controlled 
by  the  throttle  lever  so  as  to  increase  the  amount  of  heat  as  the 
throttle  is  closed.  In  warm  weather  the  diamond-shaped  shutter 
on  the  bottom  of  the  carburetor  should  be  opened  to  allow  the  hot 
exhaust  gas  to  escape  before  it  overheats  the  nozzle. 

ADJUSTMENT  OF  THE  CARBURETOR.— Turn  gasoline  ad- 
justment to  the  right  until  needle  valve  is  completely  closed.  Set 
air  adjusting  screw  so  that  end  of  the  screw  is  even  with  the  point 
of  the  ratchet  spring  just  above  it.  Open  gasoline  adjustment  by 
giving  needle  valve  one  full  turn.  Start  engine  as  usual  and  allow 
it  to  run  a  few  minutes  with  air  regulator  turned  to  "hot"  until 
engine  is  thoroughly  warmed  up. 

With  the  spark  lever  fully  retarded  turn  gasoline  adjustment  to 
the  right,  closing  needle  valve  until  engine  misses  and  then  turn  to 
left  until  engine  idles  smoothly. 

Advance  the  spark  lever  and  turn  air  adjustment  screw  to  the 
left,  a  little  at  a  time,  until  the  engine  misses  indicating  too  much 
air  and  then  turn  it  to  the  right  until  the  engine  runs  smoothly. 

To  test  the  adjustment  leave  spark  lever  advanced  and  open 
throttle  quickly.  The  engine  should  accelerate  instantly.  If  it 
skips  or  pops  back  open  gasoline  adjustment  slightly  by  turning 
needle  valve  to  the  left.  Do  not  touch  air  adjustment  again  unless 
it  appears  absolutely  necessary.  The  best  possible  adjustment  has 
been  secured  when  gasoline  adjustment  is  turned  as  far  as  possible 
to  the  right  and  air  adjustment  is  turned  as  far  as  possible  to  the  left. 
This  allows  engine  to  idle  smoothly  and  accelerate  quickly  when 
throttle  is  opened. 


CHAPTER  X 


CARBURETORS  (continued) 

The  carburetors  explained  in  this  chapter  do  not  employ  auxiliary 
air  valves.  The  methods  used  to  keep  the  proportion  of  air  and  gas 
constant  at  varying  speeds  is  explained  as  each  carburetor  is  discussed. 

STEWART— MODEL  25 

This  carburetor  is  of  the  metering  pin  type,  that  is,  it  meters  out 
the  proper  amount  of  gasoline  for  each  speed.  The  action  of  the 
carburetor  is  as  follows:  The  suction  created  in  the  inlet  manifold 
draws  air  into  the  mixing  chamber  through  air  ducts,  drilled  holes 
"H  H"  (Fig.  55).  The  same  suction  draws  a  fine  spray  of  gasoline 
through  the  aspirating  tube  "L"  into  the  mixing  chamber  and  the 
air  becomes  impregnated  with  the  gasoline  vapor.  In  order  that  the 
proportions  of  air  and  gasoline  vapor  may  be  correct  for  all  engine 
speeds  provision  is  made  by  means  of  a  valve  "A"  for  the  automatic 
admission  of  larger  quantities  of  both  air  and  gasoline  vapor  at  high 
engine  speed.  The  passages  "H  H"  are  open  at  all  times,  but  the 
valve  "  A"  is  held  to  its  seat  by  its  weight  until  the  suction,  increasing 
as  the  engine  speed  increases,  is  sufficient  to  lift  it  and  admit  a  greater 
amount  of  air  by  passing  around  "A"  at  "L"  The  valve  "A"  is 
joined  to  the  tube  "L"  hence  the  latter  is  raised  when  the  valve  is 
lifted  and  the  increase  of  proportionally  larger  quantities  of  gasoline 
is  made  possible.  This  is  accomplished  by  means  of  a  tapered  meter- 
ing pin  "P  "  normally  stationary,  projecting  upward  into  the  tube 
"L."  The  higher  the  tube  rises  the  smaller  is  the  section  of  the 
metering  pin  even  with  its  opening  and  the  greater  is  the  quantity  of 
gasoline  which  may  be  taken  into  the  tube.  The  taper  of  the  me- 
tering pin  being  carefully  designed,  the  carburetor  thus  automatically 
produces  the  correct  mixture  and  quantities  for  all  engine  speeds. 

There  is  one  adjustment  which  can  be  made  on  this  carburetor 
but  which  should  not  be  changed  unless  it  is  known  absolutely  that 
the  adjustment  is  incorrect.  The  height  of  the  metering  pin  relative 
to  the  opening  of  the  aspirating  tube  can  be  changed.  To  change  the 
fixed  " running"  position  of  the  pin  turn  the  stop  screw  to  the  right 
or  left.  Turning  this  screw  to  the  right  lowers  the  position  of  the 
metering  pin  and  turning  to  the  left  raises  it.  As  the  pin  is  lowered 


A — Air  Valve 
B — Air  Valve  Seat 
C — Float   Chamber 
D — Dash  Pot 
E — Combining  Tube 
F — Metal  Float 
G — Gasoline  Inlet  Valve 
H— Drilled   Holes 
I — Air  Passage 
K— Air  Valve  Guide 
L — Aspirating  Tube 
M — Dash  Control  Pinion 
N — Metering  Pin  Carrier 

and  Rack 

O — Mixing  Chamber 
P— Metering  Pin 
Q — Gasoline  Valve  Cap 
S — Gasoline  Passage 
V — Throttle  Valve  Lever 
Z — Filler  Screen 

AA— Air  Inlet 

CC— Filter  Cap 


Fig.  55— Stewart  Model  25 
90 


CARBURETORS  91 

more  gasoline  is  admitted  to  the  aspirating  tube  at  a  given  engine 
speed  thus  enriching  the  mixture.  A  wider  range  of  adjustment  of 
the  position  of  the  metering  pin  may  be  made  by  releasing  the  clamp 
"M"  of  the  pinion  shaft  lever  and  changing  its  position  with  relation 
to  the  shaft.  This  requires  very  careful  work  and  should  only  be 
made  in  extreme  cases.  The  metering  pin  is  also  subject  to  control 
from  the  dash  and  when  making  any  of  the  foregoing  adjustments  the 
dash  adjustment  must  be  all  the  way  in. 

In  starting  the  engine,  especially  in  cold  weather,  some  difficulty 
may  be  experienced.  To  overcome  this  difficulty  a  very  rich  mixture 
is  required  temporarily.  To  obtain  this  without  disturbing  the  regu- 
lar carburetor  adjustment  a  control  is  provided  with  an  operating 
plunger  on  the  dash  or  instrument  board.  Pulling  out  the  plunger 
operates  the  pinion  shaft  at  "M"  on  the  carburetor  and  lowers  the 
metering  pin.  This  permits  more  gasoline  to  be  drawn  through  the 
aspirating  tube  than  normally.  Though  the  quantity  of  air  drawn 
into  the  mixing  chamber  remains  the  same  a  richer  mixture  results. 
A  mixture  of  this  character  ignites  much  more  readily  than  one 
having  a  greater  proportion  of  air,  but  the  resulting  explosion  does 
not  produce  any  more  power.  Therefore,  as  soon  as  the  engine  starts 
the  plunger  at  the  dash  should  be  pushed  down. 

In  very  cold  weather,  the  dash  adjustment  should  not  be  pushed 
all  the  way  down  after  the  engine  starts  but  should  be  pushed  part 
way  back  and  left  there  until  the  engine  warms  up.  This  is  necessary 
because  the  gasoline  does  not  vaporize  as  readily  in  the  cold  weather. 

To  prime  the  carburetor  remove  Gasoline  Valve  Cap,  "Q"  and 
lift  the  float  needle  valve. 

HUDSON 

This  carburetor  is  of  the  metering  pin  type  with  eccentric  float 
chamber.  The  gasoline  enters  the  gasoline  feed  regulator  and  passes 
up  the  "V"  groove  in  the  measuring  pin.  As  the  measuring  pin  is 
lifted  it  causes  a  larger  opening  supplying  an  increased  amount  of 
gasoline.  The  suction  of  the  engine  draws  air  through  the  air  intake 
and  also  from  the  air  chamber  above  the  piston  (Fig.  56).  As  the 
air  is  drawn  from  the  air  chamber  it  causes  the  piston  to  rise  and 
lift  the  measuring  pin.  As  the  suction  increases  the  greater  will  be 
the  amount  that  the  piston  is  raised,  proportionately  increasing  the 
gasoline  supply.  As  the  piston  rises  a  larger  area  for  the  air  is 
provided,  therefore,  the  velocity  does  not  necessarily  increase  with 
the  increased  amount  of  air  passing.  If  the  amount  of  air  passing 
increases  and  the  velocity  does  not  materially  increase  it  will  require 


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CARBURETORS  93 

a  larger  opening  at  the  measuring  pin  to  keep  the  proper  propor- 
tions. This  is  automatically  controlled  by  the  piston  at  the  same 
time. 

In  case  the  resulting  mixture  is  not  correctly  proportioned  the 
gasoline  feed  regulator  can  be  adjusted.  If  it  is  lowered  it  will  cause 
richer  mixtures  and  if  it  is  raised  it  will  cause  leaner  mixtures.  This 
adjustment  is  made  by  the  feed  regulator  lever  which  is  attached  to 
a  dash  control. 

If  found  necessary  to  enrich  the  mixture  for  starting  purposes  do 
not  forget  to  readjust  it  to  the  lean  position  as  soon  as  the  engine 
warms  up.  Do  not  have  the  air  control  lever  in  the  "choke"  or 
"hot"  position  after  the  engine  is  warm.  The  increased  resistance 
to  the  air  intake  causes  a  proportionately  greater  throttle  opening 
than  is  necessary  for  the  power  developed  and  this  results  in  excessive 
gasoline  consumption. 

The  only  attention  necessary  on  this  type  of  carburetor  is  to  see 
that  the  filter  under  the  float  chamber  is  not  clogged  up,  thereby 
restricting  the  flow  of  gasoline,  and  that  the  needle  valve  is  seating 
properly  and  does  not  allow  the  gasoline  level  to  increase  and  over- 
flow at  the  regulating  sleeve.  It  is  also  advisable  to  note  the  action 
of  the  carburetor  to  make  sure  that  the  piston  valve  is  acting  smoothly 
and  responds  to  the  speed  of  the  engine.  It  is  possible  that  this 
piston  valve  may  stick  in  the  cylinder  through  an  excessive  accumu- 
lation of  dust  which  may  be  caused  by  driving  on  a  much  frequented 
road.  Provided  the  strangler  is  used  for  starting  it  is  very  likely 
this  will  not  be  noticed  as  it  is  possible  to  operate  this  carburetor 
without  any  valve  action  at  all.  However,  if  the  car  is  used  by  an 
experienced  driver  who  counts  upon  quick  acceleration  and  good 
hill  climbing  abilities  the  difference  will  be  noticed.  This  will  be 
especially  noticeable  if  driving  without  the  strangler  particularly  in 
cold  weather. 

To  free  the  valve  it  is  only  necessary  to  remove  the  cover  at  the 
top  of  the  cylinder,  withdraw  the  valve  from  its  place,  and  clean  it 
with  a  little  gasoline.  In  putting  it  back  a  few  drops  of  kerosene 
on  the  top  of  the  piston  will  help  in  flushing  down  any  sediment  or 
grit  which  the  gasoline  may  have  left. 

STROMBERG— MODEL  "M" 

This  carburetor  is  of  a  plain  tube  construction  in  which  both  the 
air  and  the  gasoline  openings  are  fixed  in  size.  The  gasoline  is 
metered  automatically  without  the  aid  of  moving  parts  by  the  suction 
of  air  velocity  past  the  jets  (Fig.  57). 


94 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


N 


M 


AIR 


Fig.  57  —  Stromberg  Model  M 

To  maintain  the  proper  proportion  of  gasoline  and  air  at  variable 
engine  speeds  an  AIR  BLED  JET  is  used  (Fig.  58).     The  principles 

of  the  Air  Bleeder  are  as  follows  : 
The  gasoline  leaves  the  float 
chamber,  passes  the  point  of  the 
high  speed  adjusting  needle,  and 
rises  through  the  channel  "B." 
Air  is  taken  in  through  the  Air 
Bleeder  "C"  and  discharged 
into  the  gasoline  channel  through 
small  holes  "D."  It  should  be 
noted  that  this  air  is  discharged 

into  the  gasoline  before  the  latter 
reacheg  ^  je(.  holeg  ^  ^  smal, 

Venturi  tube  "E."  As  the  suction  of  the  engine  increases  drawing  a 
proportionately  greater  amount  from  the  holes  at  "E"  the  propor- 
tions are  kept  constant  because  of  the  amount  of  air  bled  with  the 
gasoline  in  the  channel  "B." 

The  accelerating  well  (Fig.  59)  operates  as  follows:    The  action 
is  based  upon  the  principle  of  the  ordinary  U-tube.     If  a  U-tube 


Fig.  SS-Air  Bleeder 


CARBURETORS 


95 


contains  a  liquid  and  suction  is  applied  to  one  end  of  the  tube  the 
liquid  will  rise  in  that  arm  and  will  drop  in  the  other  arm.  Referring 
to  Fig.  59,  the  space  "F"  forms  one  arm  of  the  U-tube  and  the  space 
"B"  the  other  arm.  These  spaces  communicate  with  each  other 
through  the  holes  "G"  thus  forming  a  modified  form  of  U-tube. 

When    the    engine    is 
idling     or     retarding     in 
speed     the     accelerating 
well  or  space    "F"    fills 
P  with  gasoline.     When  the 

/  throttle  is  opened  increas- 

m£  ^ne  suction  in  the 
Venturi  tube  the  following 
takes  place:  Atmospheric 
pressure  in  the  space  "F" 
is  exerted  through  the 
bleeder  forcing  the  liquid 
down  to  join  the  regular 
flow  from  "H"  passing  up 
the  space  "B"  and  out 
into  the  high  velocity  air 
stream  through  the  small 
Venturi  tube.  While  the 
well  acts  the  flow  of  gaso- 
line is  more  than  double 
the  normal  rate  compen- 
sating for  the  lagging  of 
the  gasoline  due  to  inertia. 
Upon  close  observation  it  will  be  noticed  that  there  is  a  series  of 
small  holes  down  the  wall  of  the  well.  Referring  to  the  analogy  of 
the  U-tube  these  holes  directly  connect  the  two  arms  of  the  U-tube. 
It  is  obvious  that  the  smaller  and  fewer  these  holes,  the  faster  the 
well  will  empty  due  to  the  U-tube  suction,  and  the  larger  and  more  of 
these  holes,  the  slower  the  well  will  empty.  It  is  therefore  apparent 
that  the  rate  of  discharge  of  the  well  can  be  regulated,  as  required 
by  different  engines,  different  grades  of  gasoline,  different  altitudes, 
etc.,  by  inserting  wells  of  different  drillings.  The  action  of  tjie  well 
is  also  dependent  upon  the  size  of  the  hole  in  the  bleeder  because  the 
area  of  the  hole  of  the  bleeder  relative  to  the  areas  of  the  holes  in 
the  well  determines  the  rate  at  which  the  well  will  empty. 

The  operation  and  arrangement  for  idling  is  shown  in  Fig.  60. 
Concentric  and  inside  of  the  passage  "B"  is  located  the  IDLING 
TUBE  "J."  When  the  engine  is  idling,  that  is  when  the  throttle  is 


B 


Fig.  59 — Accelerating  Well 


H 


MOTOR  VEHICLES~AND  THEIR  ENGINES 


practically  closed,  the  action  which  takes  place  is  as  follows:  The 
gasoline  leaves  the  float  chamber,  passes  through  the  passage  "H" 
into  the  idling  tube  through  the  hole  "I,"  thence  up  through  the  idling 

jet  "L."  Air  is  drawn  through 
the  hole  "K"  and  mixes  with 
the  gasoline  to  form  a  finely 
divided  mist  which  passes  on 
to  the  jet  "L."  This  jet 
directs  the  mist,  of  gasoline  and 
air  into  the  manifold  just  above 
the  lip  of  the  throttle  valve. 
In  as  much  as  this  throttle 
valve  is  practically  closed,  the 
vacuum  created  at  the  entrance 
of  the  jet  "L"  is  very  high  and 
exceeds  8  pounds  per  square 
inch. 

It  is  obvious,  therefore,  with 
this  condition,  that  the  gasoline 
will  be  drawn  into  the  manifold 
in  a  highly  atomized  state.  It 
is  well  to  call  attention  here  to 
the  fact  that  the  LOW  SPEED 
ADJUSTING  SCREW  "F" 
operates  a  needle  valve  which 
controls  the  amount  of  air  pas- 
sing through  the  hole  "K"  and 
it  is  the  position  of  this  needle 

valve    which    determines    the 
Fig.  QO-Idling  Jet  idjing  mixture. 

As  the  throttle  is  slightly  opened  from  the  idling  position  a  suction 
is  created  in  the  throat  of  the  small  Venturi  tube  as  well  as  at  the 
idling  jet.  When  idling,  the  suction  is  greater  at  the  idling  jet,  and 
when  the  throttle  is  open  the  suction  is  greater  at  the  small  Venturi 
tube.  At  some  intermediate  position  of  the  throttle  there  is  a  time 
when  the  suction  at  the  idling  jet  is  equal  to  that  at  the  small  Venturi 
tube,  therefore,  at  this  particular  time  the  gasoline  will  follow  both 
channels  to  the  manifold.  This  condition  (Fig.  61)  lasts  but  a  very 
short  while  because  as  the  throttle  is  opened  wider  the  suction  at  the 
small  Venturi  tube  rapidly  becomes  greater  than  that  at  the  idling 
jet.  The  result  is  that  the  idling  tube  and  idling  jet  are  thrown 
entirely  out  of  action  and  the  level  of  the  gasoline  in  the  idling  tube 
drops  (Fig.  62)  when  the  throttle  is  wide  open,  in  which  case  all  of 


H 


CARBURETORS 


97 


Fig.  61— Operation  at  Slow  Speed 


Fig.  62 — Operation  at  High  Speed 


98  MOTOR  VEHICLES  AND  THEIR  ENGINES 

the  gasoline  enters  the  manifold  through  the  holes  in  the  Venturi 
tube.  With  the  throttle  in  this  position  the  accelerating  well  has 
emptied,  and  there  is  a  direct  passage  for  air  from  the  Bleeder  to  the 
gasoline  in  the  main  passage,  giving  the  "AIR  BLED  JET"  feature 
explained  before. 

TO  ADJUST  THE  CARBURETOR.— Turn  both  high  and  low 
speed  adjusting  screws  "A"  and  "B"  completely  down  so  that  the 
needle  valves  just  touch  their  respective  seats.  Then  unscrew 
(anti-clockwise)  the  high  speed  adjustment  "A"  about  three  turns 
off  the  seat,  and  turn  low  speed  adjusting  screw  "B"  (anti-clockwise) 
about  one  and  one-half  turns  off  the  seat.  The  air-horn  choke  valve 
should  be  closed  and  the  engine  is  set  for  starting.  After  the  engine 
has  warmed  up  and  the  air-horn  choke  valve  is  wide  open  the  car- 
buretor is  ready  for  adjustment. 

To  adjust  the  high-speed  adjustment  "A"  proceed  as  follows: 
Advance  the  spark  to  the  position  for  normal  running.  Set  the  gas 
lever  on  the  steering-wheel  quadrant  at  such  a  position  corresponding 
to  an  engine  speed  of  approximately  750  R.  P.  M.  Then  turn  down 
(clockwise)  on  the  high-speed  screw  "A"  gradually,  notch  by  notch, 
until  a  missing  of  the  engine  results.  Then  turn  up  or  open  the  same 
screw  (anti-clockwise)  until  the  engine  runs  at  the  highest  rate  of 
speed  for  that  particular  setting  of  the  throttle.  This  gives  an 
approximate  setting  of  the  needle  "  A." 

To  adjust  the  low-speed  adjustment  "B"  proceed  as  follows: 
Retard  the  spark  fully  and  close  the  throttle  as  far  as  possible  without 
causing  the  engine  to  come  to  a  stop.  If  upon  idling  the  engine  tends 
to  "roll"  or  "load"  it  is  an  indication  that  the  mixture  is  too  rich 
and  therefore  the  low-speed  adjusting  screw  "B"  should  be  turned 
away  from  the  seat  (anti-clockwise)  thereby  permitting  the  entrance 
of  more  air  into  the  idling  mixture.  This  rolling  of  the  engine  might 
also  be  due  to  uneven  compression  in  the  cylinders,  or  to  the  lack  of 
compression  in  one  or  more  of  the  cylinders.  The  low-speed  adjust- 
ment is  best  made  by  carefully  observing  the  smoothness  with  which 
the  engine  revolves  when  idling,  and  can  be  properly  obtained  by 
turning  the  screw  "B"  up  or  down,  notch  by  notch,  until  the  best 
idling  prevails.  It  is  safe  to  say  that  the  best  idling  results  will  exist 
when  the  screw  "B."  is  not  much  more  or  less  than  one  and  one-half 
turns  off  the  seat 

After  satisfactory  adjustments  have  been  made  with  the  motor 
vehicle  stationary  it  is  most  important  and  advisable  to  take  the 
vehicle  out  on  the  road  for  further  observation  and  finer  adjustments. 
If  upon  rather  suddenly  opening  of  the  throttle  the  engine  backfires 
it  is  an  indication  that  the  high-speed  mixture  is  too  lean  and  in  this 


CARBURETORS 


99 


case  the  adjusting  screw  "A"  should  be  opened  one  notch  at  a  time 
until  the  tendency  to  backfire  ceases.  On  the  other  hand  if  when 
running  along  with  open  throttle  the  engine  " rolls"  or  "loads"  it  is 
an  indication  that  the  mixture  is  too  rich  and  this  is  overcome  by 
turning  the  highspeed  screw  "A"  down  (clockwise)  until  this  loading 
is  eliminated. 

•       ZENITH— MODEL  "L" 

This  carburetor  is  of  the  compound  nozzle  type  and  to  fully  under- 
stand its  operation  a  detailed  description  of  the  principle  upon  which 
it  is  constructed  will  be  given. 

As  was  explained  with  a  simple  construction  of  carburetor  having 
no  regulation  (Fig.  41)  when  the  suction  increases  the  air  and 
gasoline  increases  but  the  proportion  of  gasoline  increases  a  greater 
amount  than  the  air,  therefore,  the  mixture  becomes  richer. 


F 


Fig.  63 — Constant  Flow  Nozzle 


If  a  jet  such  as  shown  in  Fig.  63  be  used  in  which  the  opening 
at  "I"  is  smaller  than  the  opening  at  the  nozzle  "H"  the  follow- 
ing condition  will  exist.  When  the  car  has  been  standing  the  well 
"J"  and  nozzle  "H"  will  fill  up  to  the  level  in  the  float  chamber 
"F."  Although  the  suction  is  not  high  at  ordinary  speeds  say  400 
R.  P.  M.  yet  it  could  take  up  more  gasoline  from  "H"  than  is 
permitted  to  flow  through  "I."  Air  is  also  drawn  up  through  the 
nozzle  from  the  open  well  and  the  mixture  is  too  lean  for  proper 
results. 

As  the  speed  of  the  car  increases  the  suction  is  greater  and  the 
quantity  of  air  increases  while  the  gasoline  remains  the  same  because 


100 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


the  tiny  stream  at  "I"  is  independent  of  the  suction  at  "H"  (the 
suction  at  "H"  is  not  transmitted  to  "I"  because  the  open  well 
"J"  allows  air  to  satisfy  this  suction).  The  mixture  becomes  leaner 
and  leaner  as  the  speed  or  suction  increases,  the  action  being  directly 
opposite  to  that  of  the  simple  jet  construction. 


E     K' 

Fig.  64 — Compound  Jet 

In  Fig.  64  a  construction  is  shown  with  the  jets  combined  showing 
the  level  of  the  gasoline  when  the  engine  is  at  rest.  The  simple  jet 
"G"  is  supplied  through  the  pipe  "E"  and  compounded  with  the 
jet  "H"  which  is  supplied  by  the  pipe  "K"  from  open  well  "J"  and 
compensator  "I." 


E1    K1 

Fig.  65 — Operation  at  Low  Speed 

Fig.  65  shows  the  condition  when  the  engine  is  under  load  at  400 
R.  P.  M.  with  wide  open  throttle.  This  suction  is  not  very  strong, 
but  it  is  lifting  gasoline  from  nozzle  #W.  and  also  from  nozzle  "H," 

ft* 


CARBURETORS 


101 


the  latter  being  fed  from  open  well  "J."  "T&e  action  of  "the  com- 
pensator "I"  has  held  down  the  supply  algasqllntf  &$ifap  av^l  has 
emptied. 

Fig.  66  shows  the  condition 
with  the  engine  turning  1600 
R.  P.  M.  The  suction  has 
greatly  increased  as  shown  by 
the  arrows  drawing  more  gaso- 
line from  nozzle  "G,"  nozzle 
"H"  however,  still  gives  the 
same  measured  amount  because 
of  the  action  of  the  compensa- 
tor "I." 

The   compound   nozzle    re- 
ceives  its   gasoline   from    two 
sources.     At    any   speed   both 
sources  of  supply  are  in  action.       Fig.  66 — Operation  at  High  Speed 
The  main  jet   "G"    (the   one 

controlled  by  suction)  is  selected  of  the  proper  size  to  give 
just  about  enough  gasoline  at  high  suction.  At  low  suction  it  will, 
of  course,  be  deficient.  This  unavoidable  defect  of  one  nozzle,  start- 
ing poor  and  growing  richer  until  it  is  almost  right  at  high  suction,  is 
compensated  for  by  the  peculiarity 
of  the  other  jet  "H"  which  also 
starts  poor  and  keeps  growing 
poorer.  The  compensator  "  I "  sup- 
ports the  main  nozzle  "G"  at  low 
suction  when  it  is  most  needed. 
One  supplements  the  other  so  that 
at  every  engine  speed  there  is  a 
constant  ratio  of  air  and  gasoline 
to  stimulate  efficient  combustion. 

IDLING  DEVICE.— At  low 
speed  when  the  butterfly  throttle 
valve  "T"  is  nearly  closed  the 
main  jet  and  cap  jet  gives  but  little 
or  no  gasoline,  but  as  there  is  con- 
siderable suction  on  the  edge  of  the 
butterfly,  the  gasoline  is  drawn 
through  the  idling  device.  This 
device  (Fig.  67)  consists  of  the 
idling  tube  "J"  within  the  secondary 
well  "P"  inserted  in  the  first  well  Fig.  67— Idling  Device 


102 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


at  the  bottom  of  whic^the  compensator  "I"  is  located  and  which 
is  openitkxjat^spbpi-e  pressure  through  holes  "A." 

Gasoline  from  the  compensator  "I"  flows  through  the  calibrated 
hole  in  the  bottom  of  the  secondary  well  "P"  which  in  turn  is  ad- 
justably open  to  the  air  through  the  idling  screw  "O."  The  idling 
tube  "J"  leads  to  a  hole  located  at  the  edge  of  the  butterfly  throttle 
valve  where  the  suction  is  most  strongly  felt.  This  suction  lifts  the 
gasoline  through  the  idling  tube  and,  in  combination  with  the  air 
passing  the  butterfly  valve,  forms  the  idling  mixture. 

There  are  four  adjustments  which  are  possible  with  this  type  of 
carburetor. 

1.  Choke  tube  "X." 

2.  Main  jet  "G." 

3.  Compensator  "  I." 

4.  Regulator  screw  "0." 

CHOKE  TUBE  TOO  LARGE.— The  "pick  up"  will  be  defective 
and  cannot  be  bettered  by  the  use  of  a  larger  Compensator.  Slow 


Fig.  68— Zenith  Model  L 


CARBURETORS  103 

speed  running  will  not  be  very  smooth.  The  engine  will  have  a 
tendency  to  "load-up"  under  a  hard  pull  and  at  high  speed  the 
exhaust  will  be  of  an  irregular  nature.  This  "loading-up"  will  be 
much  worse  if  the  manifold  is  too  cold. 

CHOKE  TUBE  TOO  SMALL.— The  effect  of  a  small  Choke  Tube 
is  to  prevent  the  engine  from  taking  a  full  charge  with  the  throttle 
opened  wide.  The  "pickup"  will  be  very  good  but  it  will  not  be 
possible  to  get  all  the  speed  of  which  the  car  is  capable.  Remember 
that  when  the  Choke  (Venturi  tube)  is  increased  more  air  is  admitted 
and  the  mixture  is  correspondingly  thinned.  The  influence  of  the 
Main  Jet  is  mostly  felt  at  high  "speed. 

MAIN  JET  TOO  LARGE.— At  high  speed  on  a  level  road  it  will 
give  the  usual  indications  of  a  rich  mixture;  irregular  running, 
characteristic  smell  from  the  exhaust,  firing  in  the  muffler,  sooting 
up  at  the  spark  plugs,  and  low  mileage. 

MAIN  JET  TOO  SMALL.— The  mixture  will  be  too  lean  at  high 
speed  and  the  car  will  not  attain  its  maximum  speed.  There  may 
be  back-firing  at  high  speed,  but  this  is  not  probable  especially  if  the 
Choke  and  main  jet  are  according  to  the  factory  setting.  This  back- 
firing is  more  often  due  to  large  air  leaks  in  the  intake  or  valves  or  to 
defects  in  the  gasoline  line. 

The  compensator  size  is  best  tried  out  on  a  long  gradual  hill  of 
such  a  slope  that  the  engine  will  labor  rather  hard  to  make  it  on  high 
gear.  A  long,  even,  hard  pull  of  this  sort  taxes  the  efficiency  of  the 
Compensator  to  the  utmost  and  will  indicate  readily  the  correctness 
of  its  size. 

COMPENSATOR  TOO  LARGE.— This  will  cause  too  rich  a 
mixture  on  a  hard  pull.  It  will  give  the  same  indication  as  for  rich 
mixture  at  high  speed  on  the  level. 

COMPENSATOR  TOO  SMALL.— This  will  cause  too  lean  a 
mixture  making  the  engine  liable  to  miss  and  give  jerky  action  of 
the  car  on  a  hard  pull. 

IDLING  DEVICE  IS  TOO  SMALL.— It  will  be  impossible  to 
obtain  a  satisfactory  mixture  except  by  turning  the  Idling  (adjusting) 
Screw  all  the  way  in.  In  this  event  put  in  a  larger  Idling  Device. 

IDLING  DEVICE  IS  TOO  LARGE.— It  will  be  impossible  to 
obtain  a  satisfactory  mixture  unless  the  Idling  Screw  is  turned  out  as 
far  as  possible.  In  this  case  put  in  a  smaller  Idling  Device. 

It  has  been  found  from  practice  that  it  is  rarely  necessary  to  make 
adjustments  on  this  carburetor  as  the  conditions  are  carefully  cal- 
culated when  installing  the  carburetor  by  the  engine  manufacturer, 
however,  in  a  few  cases  where  the  climatic  conditions  or  the  grade  of 


104  MOTOR  VEHICLES  AND  THEIR  ENGINES 

gasoline  vary  greatly  from  the  ordinary  standards,  the  Compensator 
"I"  and  the  Jet  "G"  may  have  to  be  changed. 

RAYFIELD 

The  Rayfield  carburetors  are  made  in  two  types,  models  G  and 
L.  The  difference  is  that  model  G  is  water-jacketed  (Fig.  69). 
These  carburetors  are  of  the  mixed  type,  having  both  auxiliary  air 
valves  and  metering  pins.  The  gasoline  supply  enters  through  the 
gasoline  intake  passing  the  needle  valve  which  is  operated  by  the 
float.  Gasoline  is  supplied  from  the  float  chamber  to  the  two 
nozzles,  marked  in  Fig.  69  as  "spray  nozzle"  and  " metering  pin 
nozzle." 

Air  enters  the  mixing  chamber  from  three  sources:  Through  a 
constant  air  opening  which  is  a  hole  in  the  side  of  the  carburetor  so 
that  the  air  in  entering  the  mixing  chamber  passes  the  spray  nozzle. 
Air  also  enters  through  the  upper  automatic  air  valve,  this  air  passing 
the  metering  pin  nozzle.  The  lower  air  valve  admits  air  directly  to 
the  mixing  chamber  and  is  operated  by  levers  which  are  controlled 
by  the  automatic  air  valve. 

The  operation  of  this  carburetor  is  as  follows:  With  a  closed 
throttle  and  the  engine  idling,  air  enters  through  the  constant  air 
opening  picking  up  gasoline  at  the  spray  nozzle.  As  the  speed  is 
increased  and  the  throttle  opened  wide,  the  increased  suction  will 
cause  the  automatic  air  valve  to  open.  This  valve  in  opening  causes 
the  lower  air  valve  to  open  and  at  the  same  time  forces  down  the 
metering  pin  which  increases  the  opening  at  the  metering  pin  nozzle, 
causing  a  greater  amount  of  gasoline  to  be  supplied.  When  suddenly 
accelerating  the  operation  is  as  follows:  The  automatic  air  valve 
opening  suddenly  causes  the  dash-pot  piston  to  force  gasoline  out 
of  the  metering  pin  nozzle,  thus  enriching  the  mixture  which  will 
compensate  for  the  lag  of  the  gasoline  due  to  inertia. 

ADJUSTING  LOW  SPEED.— With  throttle  closed,  dash  control 
down,  close  nozzle  needle  by  turning  low  speed  adjustment  to  the 
left  until  block  "U"  slightly  leaves  contact  with  cam  "M."  Then 
turn  to  the  right  about  3  complete  turns.  Start  engine  and  allow 
it  to  run  until  warmed  up.  Then  with  retarded  spark  close  throttle 
until  engine  runs  slowly.  With  the  engine  thoroughly  warm  make 
final  low  speed  adjustment  by  turning  low  speed  screw  to  left  until 
engine  misses  and  then  turn  to  right  a  notch  at  a  time  until  engine 
idles  smoothly.  If  the  engine  does  not  throttle  low  enough  turn 
stop  arm  screw  "A"  to  the  left  until  the  engine  runs  at  the  lowest 
number  of  revolutions  desired. 


HIGH    SPEED 
ADJUSTMENT 

TURN  TO  RIGHT  FOR. 

MORE  GAS 


LOW  SPEED 
ADJUSTMENT 


(LOWER  AIR  VALVE] 
MODEL  G 


Fig.  69 — Rayfield  Carburetor 

105 


106 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


ADJUSTING  HIGH  SPEED.— Advance  spark  about  one-quarter. 
Open  throttle  rather  quickly.  Should  engine  miss,  it  indicates  a 
lean  mixture.  Correct  this  by  turning  high  speed  adjustment  screw 
to  the  right  one  notch  at  a  time  until  the  throttle  can  be  opened 
quickly  without  the  engine  missing.  If  "loading"  or  "choking"  is 
experienced  when  running  under  heavy  load  with  throttle  wide  open, 
it  indicates  too  rich  a  mixture.  This  can  be  overcome  by  turning 
high  speed  adjustment  to  the  left. 

TO  START  ENGINE  WHEN  COLD.— First,  close  throttle  and 
pull  dash  control  all  way  up.  Second,  when  engine  starts  open 
throttle  slightly  and  push  dash  control  J4  way  down.  Third,  as 
engine  warms  up  push  control  down  gradually  as  required.  When 
thoroughly  warm  push  dash  control  all  way  down.  When  engine  is 
warm  it  is  necessary  to  pull  dash  control  only  part  way  up  for  starting. 

SCHEBLER— MODEL  A,  SPECIAL 

This  carburetor  is  of  the  plain  tube  type  with  eccentric  float 
chamber.  All  the  air  enters  at  "I"  and  passes  through  the  Venturi 
tube  past  the  nozzle  to  the  inlet  manifold  (Fig.  70).  The  gasoline 
supply  enters  at  "12"  passing  through  the  screw  "11"  and  enters 
the  float  chamber.  The  proper  level  is  maintained  in  the  usual 
manner  by  a  float  "15"  operating  a  needle  valve  "13."  From  the 
float  chamber  the  gasoline  has  two  paths;  one  is  past  Idle  adjusting 
needle  valve  "9"  to  passage  "7,"  the  other  is  past  main  fuel  adjusting 
needle  valve  "14." 

When  starting,  the  choke  should  be  closed  (Fig.  71),  especially  in 
cold  weather  and  the  throttle  "19"  nearly  closed.  This  shuts  off 
the  air  supply  and  the  suction  causes  gasoline  to  be  drawn  through 

passage  "7"  and  out  the 
opening  just  above  the 
throttle.  Some  gasoline  will 
also  be  drawn  from  the  three 
holes  "21"  and  the  lip  "6." 
This  gives  a  rich  mixture 
which  makes  starting  easy. 
When  running  idle  the 
throttle  is  closed.  This  only 
permits  a  small  amount  of 
air  to  pass  through  the 
Venturi  tube,  its  velocity  not 
being  sufficient  to  draw  gaso- 
Fig.  71 — Operation  Choked  line  from  the  main  jet.  The 


107 


108  MOTOR  VEHICLES  AND  THEIR  ENGINES 


Fig.  72 — Operation  Running  Idle 


Fig.  73 — Operation  Under  Partial 
Load 


greatly  restricted  area  at  the  throttle  creates  a  suction  at  the  open- 
ing of  passage  "7."  Some  of  the  air  entering  will  pass  under  the 
edge  of  the  Venturi  tube  (Fig.  72)  into  passage  "18,"  thence  through 
passage  "7"  mixing  with  the  gasoline.  This  mixture  is  delivered 
through  the  opening  just  above  the  throttle. 

As  the  throttle  is  opened  the  amount  of  mixture  drawn  through 
the  Venturi  tube  is  increased.  The  velocity  of  the  air  now  being 
sufficient  to  cause  a  suction  which  will  draw  fuel  through  the  three 
holes  "21"  (Fig.  73).  The  incoming  air  strikes  the  projecting  lip 

on  the  nozzle  housing  and  due 
to  its  velocity  enters  the  hole 
"6."  Due  to  the  U-tube  con- 
struction contained  in  the 
nozzle  housing,  the  level  of 
gasoline  in  the  arm  connected 
to  the  opening  "6"  will  be 
lowered  uncovering  holes  be- 
tween this  arm  and  arm  "20." 
As  these  holes  are  uncovered 
the  air  passes  through  them 
mixing  with  gasoline  in  passage 
"20."  Instead  of  pure  gaso- 

Fig.  74— Operation  Under  Full  Load  line   beinS   delivered    at    holes 

"21,"  a  spray  of  air  and  gasoline 

is  delivered  which  mixes  with  the  air  being  drawn  through  the 
Venturi  tube.  Some  mixture  may  be  delivered  by  the  idling  jet, 
decreasing  as  the  throttle  is  opened. 

When  the  throttle  is  wide  open  (Fig.  74)  the  increased  amount  of 
air  passing  through  the  Venturi  tube  causes  a  much  greater  suction 


CARBURETORS  109 

at  the  holes  ".21,"  likewise  the  pressure  at  the  hole  "6"  is  increased 
causing  the  level  to  be  lowered  still  further  in  the  U-tube.  This 
permits  more  air  to  be  drawn  through  the  communicating  holes 
mixing  with  the  gasoline  in  the  passage  "20."  Thus  the  proportion 
of  air  and  gasoline  delivered  to  the  mixing  chamber  is  kept  constant 
as  an  increasing  amount  is  drawn  through  the  holes  "21."  If  only 
pure  gasoline  was  drawn  the  mixture  would  become  richer  but  as 
both  air  and  gasoline  are  drawn  from  holes  "21,"  this  air  bleeding 
keeps  the  mixture  constant  at  all  speeds. 

ADJUSTMENT.— There  are  but  two  adjustments  on  this  car- 
buretor both  of  which  control  the  amount  of  gasoline  supplied.  The 
idle  adjusting  needle  valve  "9"  regulates  the  supply  of  gasoline  for 
idling  and  the  main  needle  valve  "14"  regulates  the  amount  of 
gasoline  supplied  to  the  main  fuel  nozzle  "4." 

Screw  out  both  Adjusting  Needles  several  turns.  Start  the  en- 
gine with  the  throttle  slightly  open.  Slowly  turn  the  Idle  Adjusting 
Head  "17"  to  the  right  or  towards  the  "less  gas"  position  as  indi- 
cated by  the  dial  until  the  engine  runs  smoothly.  Adjust  the  engine 
speed  for  running  idle  by  means  of  the  throttle  lever  Stop  Screw  on 
the  throttle  lever.  Open  the  throttle  wide  allowing  the  governor  to 
regulate  the  engine  speed  and  with  a  retarded  spark  turn  the  Main 
Gas  Adjusting  Head  "16"  toward  the  "less  gas"  direction  until  the 
engine  begins  to  miss  or  backfire.  Turn  the  adjusting  head  in  the 
"more  gas"  direction  just  sufficient  to  stop  the  engine  missing  or 
backfiring.  These  adjustments  should  produce  a  good  mixture. 

For  starting  or  warming  up  with  the  present  day  fuel  it  is  almost 
always  necessary  to  use  the  air  choke  until  proper  operating  tem- 
perature is  obtained.  The  engine  will  start  readily  with  the  choke 
closed  one-half  to  three-quarters  of  the  way.  When  the  weather  is 
very  cold  it  may  be  necessary  to  close  the  choke  entirely,  but  this 
should  be  done  only  for  an  instant,  as  it  cuts  off  all  the  air  and  delivers 
practically  raw  gasoline. 

WHITE 

The  White  is  an  eccentric  float,  multi-jet  type  of  carburetor  (Fig. 
75).  Air  enters  at  opening  "47,"  which  is  .provided  with  a  choke 
"42."  The  gasoline  flows  from  the  float  chamber  to  the  low  speed 
nozzle  "29"  and  high  speed  nozzle  "28."  A  small  drilled  hole  "62" 
in  the  side  of  low  speed  nozzle  "29"  near  its  base  supplies  gasoline 
to  a  passage  leading  to  a  vertical  well  "64"  in  the  side  of  the  car- 
buretor body. 

The  nozzles  are  incased  in  nozzle  sheaths  "34"  and  "33."  Low 
speed  nozzle  sheath  "34"  is  open  at  the  top  but  closed  at  the  bottom 


110 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


to  air  entering  at  "47."  High  speed  nozzle  sheath  "33"  is  open  at 
the  top  and  drilled  with  holes  "63"  at  the  bottom  permitting  some 
of  the  air  to  be  drawn  up  inside  the  sheath  discharging  at  its  top. 
Ths  starting  nozzle  "65"  dips  into  the  vertical  well  "64"  and  sup- 


34       33 


Fig.  75— The  White  Carburetor 

plies  gasoline  through  a  small  drilled  hole  just  above  the  throttle 
valve.  Screened  hole  "106"  opening  into  the  top  of  the  well,  main- 
tains atmospheric  pressure  at  all  times.  The  throttle  valve  "2"  is 
of  the  barrel  type,  consisting  of  a  metal  cylinder  with  twin  openings 
cut  through  it  of  the  proper  shape  to  admit  mixture.  As  the  throttle 
is  revolved  on  its  axis  the  opening  from  the  low  speed  nozzle  is 
gradually  uncovered.  At  a  certain  point  the  opening  to  the  high 
speed  nozzle  is  uncovered  and  at  wide  open  throttle  position,  both 
passages  are  completely  uncovered.  A  screw  "36"  is  provided 
regulating  the  amount  of  air  supplied  with  the  throttle  closed  and 
the  engine  idling. 


A — IDLE 


S  L          P 

B — Low  SPEED 


C — MEDIUM  SPEED 


H  L         P 

D — HIGH  SPEED 


Fig.  76 — Operation  of  White  Carburetor 
ill 


112  MOTOR  VEHICLES  AND  THEIR  ENGINES 

Referring  to  the  diagrams  in  Fig.  76  the  operation  of  the  car- 
buretor is  as  follows: 

For  idling  or  starting  the  throttle  is  completely  closed  (Fig.  76 A). 
Suction  in  the  intake  manifold  causes  a  reduction  in  pressure  above 
the  throttle  "T."  Atmospheric  pressure  exerted  at  the  top  of  well 
"  W"  causes  gasoline  to  rise  in  the  starting  nozzle  "N."  At  the  same 
time,  air  is  drawn  past  the  regulating  screw  (not  shown)  and  through 
the  drilled  hole  "D"  producing  a  mixture  for  starting  and  idling. 
The  choke  must  be  closed  when  starting,  reducing  to  a  minimum  the 
amount  of  air  drawn  through  "D." 

'  For  low  speed  the  throttle  is  turned  so  that  the  low  speed  passage 
is  partially  uncovered  (Fig.  76B).  A  considerable  volume  of  air  is 
drawn  past  the  low  speed  nozzle  sheath  "S"  causing  low  speed 
nozzle  "L"  to  deliver  gasoline  which  passes  out  the  opening  at  the 
top  of  the  sheath  and  mixes  with  the  incoming  air.  The  well  "W" 
is  almost  immediately  emptied,  a  small  quantity  of  air  probably 
being  drawn  in  through  the  passage  "P."  The  high  speed  nozzle 
"H"  is  still  completely  covered. 

As  the  throttle  is  turned  to  the  medium  speed  position,  the  low 
speed  passage  is  further  uncovered  and  the  high  speed  passage  is 
uncovered  slightly  (Fig.  76C).  The  low  speed  nozzle  "L"  functions 
as  before,  the  increased  suction  causing  it  to  deliver  more  mixture. 
Additional  air  and  gasoline  is  supplied  through  the  partially  un- 
covered high  speed  passage,  air  passing  in  at  the  bottom  of  the  sheath 
"R." 

As  the  throttle  is  turned  to  the  high  speed  position,  both  low  and 
high  speed  passages  are  completely  uncovered,  bringing  both  nozzles 
fully  into  action  (Fig.  76D).  The  maximum  volume  of  air  is  drawn 
through  both  the  low  and  high  speed  openings.  Low  speed  nozzle 
"L"  draws  as  much  air  as  possible  through  passage  "P"  and  high 
speed  nozzle  "H"  delivers  its  maximum.  It  is  probable  that  the 
air  passing  through  the  sheath  "R"  increases  the  suction  on  high 
speed  nozzle  "H."  If  the  throttle  is  suddenly  opened  wide  a  large 
volume  of  air  will  rush  in  past  "R"  before  a  flow  of  gasoline  from 
"H"  is  established.  This  will  cause  the  engine  to  "die." 

ADJUSTMENT.— The  only  adjustment  on  this  carburetor  is 
made  by  the  Idle  Adjusting  Screw  "36"  with  the  engine  running 
and  the  car  standing  still.  If  there  is  too  much  air,  this  screw  should 
be  turned  to  the  right  or  in.  If  there  is  not  enough  air,  it  should  be 
turned  to  the  left  or  out.  Further  regulation  of  the  quantity  of 
air  and  gasoline  for  every  position  of  the  throttle  valve  is  automatic. 
Too  rich  a  mixture  may  be  caused  by  dirt  in  the  air  inlet  screens. 
These  should  be  kept  clean. 


CARBURETORS  113 

In  extreme  cases,  the  nozzles  "34"  and  "33"  may  be  replaced  by 
others  of  different  drillings.  Both  the  hole  at  the  top  of  low  speed 
nozzle  "34"  and  hole  "62"  in  its  side  near  the  base  vary  in  size. 
The  high  speed  nozzle  "33"  is  seldom  changed. 

The  air  coming  in  at  "47"  is  supplied  through  a  tube  running 
to  a  stove  on  the  exhaust  pipe.  A  shutter  "45"  is  provided  to  regu- 
late the  temperature  of  this  air.  This  shutter  should  be  closed  in 
winter  and  open  in  summer.  Additional  heat  is  supplied  by  pumping 
warm  water  through  the  jacket  on  the  inlet  manifold  "50." 


CHAPTER  XI 


PUDDLE  TYPE  CARBURETORS 

The  carburetors  explained  in  the  preceding  chapters  are  of  the 
sprayer  type,  that  is,  a  nozzle  is  used  to  supply  the  gasoline  to  the 
mixing  chamber  in  the  form  of  a  spray.  There  are  certain  types  of 
carburetors  which  do  not  use  a  nozzle  but  allow  the  incoming  air  to 
pass  over  the  surface  of  a  puddle  of  gasoline  and  draw  off  vapor 
carrying  it  to  the  mixing  chamber.  For  this  reason  they  are  called 
the  puddle  type  of  carburetor.  The  most  common  of  these  types 
will  be  explained  in  this  chapter. 

KINGSTON— MODEL  "Y" 

This  carburetor  was  used  on  Ford  Cars  and  is  of  the  puddle  type. 
The  gasoline  enters  the  float  chamber  passing  the  gasoline  supply 
valve  until  the  proper  level  is  attained.  The  gasoline  from  the  float 
chamber  passes  the  valve  and  fills  the  recess  directly  around  it 
(Fig.  77). 

The  mixing  chamber  is  of  a  peculiar  form,  so  designed  that  all 
the  primary  air  must  pass  over  the  small  pool  of  gasoline  at  the 
bottom  of  the  mixing  chamber  before  it  reaches  the  engine.  The 
amount  of  gasoline  supplied  to  the  mixture  may  be  varied  by  regu- 
lating the  needle  valve. 

At  low  speed  all  the  air  entering  passes  through  the  main  air  inlet 
(primary  air)  and  picks  up  the  gasoline  carrying  it  to  the  cylinders. 
As  the  speed  increases  this  mixture  becomes  richer  and  additional 
air  must  be  supplied  which  does  not  pass  over  the  puddle  of  gasoline. 
The  additional  air  is  admitted  through  the  auxiliary  air  duct  passing 
the  auxiliary  air  valves  of  the  ball  type  and  entering  the  inlet  mani- 
fold. These  balls  are  so  arranged  that  as  the  suction  increases  they 
lift  in  turn  from  their  seats  admitting  a  greater  amount  of  air. 

The  only  adjustment  on  this  carburetor  is  the  needle  valve  which 
when  turned  to  the  right  causes  the  mixture  to  become  leaner  and 
when  turned  to  the  left  causes  richer  mixtures. 

HOLLEY— MODEL  "S" 

This  carburetor  is  of  the  puddle  type  with  concentric  float  (Fig. 
78).  The  gasoline  enters  the  gasoline  inlet  pipe  (Fig.  79)  passing 

114 


PUDDLE  TYPE  CARBURETORS 


115 


NEEDLE  VALVE 


COCKING   SCREW 

CHOKE 

THROTTLE 

LEVER 

AUXILIARY 
AIR   DUCT 


OCKING  SCREW 
ADJUSTING   SCREW 
THROTTLE  LEVER 


OVERFLOW  TUBE 


DRAIN  COCK 


Fig.  77— Kingston  Model  Y 


6  A  SO L 

NEEDLE    VALV£. 


TH e  rue L  ANQ  A.IA 
TAKf/V   THROUGH  THE 

T(J0£.QLjr 
TO    THROTTLf. 


Fig.  1%—Holley  Model 


116 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


the  float  needle  valve  in  entering  the  float  chamber.  From  the  float 
chamber  the  gasoline  passes  through  the  holes  "E"  to  the  needle 
valve  "F."  The  float  level  is  so  set  that  the  gasoline  rises  past  the 
needle  valve  and  sufficiently  fills  the  cup  "G"  to  submerge  the  lower 
end  of  the  small  copper  tube  "H." 


Fig.  79— Side  View  of  Holley 

The  air  enters  from  only  one  source,  the  air  intake,  there  being  no 
auxiliary  air  valves  in  the  carburetor.  All  the  air  entering  the  car- 
buretor must  pass  over  the  surface  of  the  puddle  of  gasoline  at 
"G."  The  needle  valve  "F"  regulates  the  amount  of  gasoline 
supplied  to  this  well. 

The  tube  "H"  conducts  gasoline  from  the  well  "G"  to  a  point 
just  beyond  the  throttle  valve.  This  arrangement  assists  in  supply- 
ing a  mixture  for  running  idle  with  closed  throttle. 

For  facilitating  starting  in  cold  weather  a  choke  is  placed  in  the 
air  passage  to  cause  a  slightly  richer  mixture. 

The  only  adjustment  on  this  carburetor  is  the  needle  valve  and 
when  turned  to  the  right  will  cause  leaner  mixtures  and  when  turned 
to  the  left  will  give  richer  mixtures. 


CHAPTER  XII 


MAGNETISM 

In  order  to  thoroughly  understand  ignition,  starting,  and  lighting 
systems,  a  preliminary  knowledge  of  magnetism  and  elementary 
electricity  is  necessary.  Only  the  most  simple  and  fundamental 
electrical  principles  will  be  taken  up  but  it  will  be  necessary  that  this 
and  the  following  chapter  be  thoroughly  understood  or  trouble  will 
be  encountered  when  the  electrical  apparatus  used  on  a  motor 
vehicle  is  studied.  The  preliminary  discussion  will  be  divided  into 
two  parts,  a  chapter  on  Magnetism  and  a  chapter  on  Elementary 
Electricity. 

The  name  magnet  was  first  applied  to  certain  brown  colored 
stones  taken  from  the  earth  which  possessed  the  peculiar  property 
of  attracting  small  pieces  of  iron  ore.  When  freely  suspended  by  a 
string  at  the  center  this  stone  possessed  the  important  property  of 
pointing  north  and  south,  hence,  it  was  given  the  name  of  "lode- 
stone"  (meaning  leading  stone).  Hence,  a  magnet  may  be  defined 
as  a  piece  of  steel  or  other  substance  which  possesses  the  properties 
of  attracting  other  pieces  of  steel  or  iron,  and  of  pointing  north  and 
south  when  freely  suspended  in  a  horizontal  position. 

The  compass  needle  is  nothing  more  than  a  small  bar  magnet 
pivoted  at  the  center  so  that  it  is  free  to  turn  in  any  direction  like 
the  lodestone.  It  will  always  point  north  and  south,  the  same  end 
pointing  north  each  time.  The  ends  of  a  magnet  are  termed  its 
poles.  The  point  midway  between  them  is  known  as  the  neutral 
point.  The  end  of  a  compass  needle  which  points  to  the  north  is 
termed  the  north  pole  while  the  opposite  end  is  called  the  south  pole. 
The  north  pole  of  a  magnet  is  generally  marked  in  some  manner  to 
distinguish  it  from  the  south  pole. 

Magnets  are  of  two  kinds,  permanent  and  temporary.  Per- 
manent magnets  are  either  bar  or  horseshoe,  the  names  arising  from 
their  shape.  A  permanent  magnet  must  be  a  piece  of  steel  which 
has  been  magnetized  and  which  retains  its  magnetism  indefinitely. 
A  temporary  magnet  may  be  a  piece  of  iron  under  the  influence  of  a 
permanent  steel  magnet  or  temporarily  magnetized  by  electric 
current  (electro-magnet). 

There  is  a  distinction  between  substances  which  are  magnetic 
and  which  are  nonmagnetic.  Iron  and  steel  are  the  only  two  sub- 

117 


118 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


stances  which  manifest  these  properties  to  any  great  extent.  Two 
other  metals,  nickel  and  cobalt,  are  very  slightly  magnetic.  For  prac  - 
tical  purposes  all  other  substances  such  as  copper,  lead,  gold,  brass, 
bronze,  wood,  rubber,  glass,  etc.,  cannot  be  magnetized  and  are  there- 
fore nonmagnetic.  Magnetic  influences  will  take  place  through  these 
substances. 

A  distinction  must  also  be  made  between  magnets  and  magnetic 
substances.  A  magnet  attracts  only  at  its  poles,  each  of  which  pos- 
sesses opposite  properties.  A  piece  of  iron  will  be  attracted  by  a 
magnet  no  matter  what  part  of  it  is  approached  to  the  magnet  but 
it  does  not  possess  fixed  poles  or  a  neutral  point  while  a  magnet 
always  has  two  poles  and  a  neutral  point. 


Fig.  80 — Field  Surrounding  a  Bar  Magnet 

Surrounding  any  magnet  there  exists  what  is  known  as  the  mag- 
netic field.  It  is  invisible  and  in  fact  is  not  perceptible  to  any  of  the 
senses.  That  it  does  exist  can  be  proved  by  placing  a  piece  of  paper 
over  the  magnet  and  sifting  iron  filings  over  it.  The  magnetic  force 
which  permeates  the  space  immediately  surrounding  the  magnet 
causes  the  filings  to  arrange  themselves  in  a  certain  definite  manner 
indicating  the  nature  of  the  force,  its  direction,  and  distribution. 
The  magnetic  force  is  not  the  same  at  all  distances  but  decreases  as 
the  distance  from  the  magnet  increases.  Fig.  80  shows  the  magnetic 
field  existing  about  a  bar  magnet  while  Fig.  81  shows  the  magnetic 
field  of  a  horseshoe  magnet. 

It  is  assumed  that  the  magnetic  lines  of  force  (Figs.  80  and  81) 
emanate  from  the  north  pole  of  the  magnet,  pass  through  the  sur- 
rounding medium,  re-enter  at  the  south  pole  and  complete  the  circuit 
by  passing  from  the  south  to  the  north  pole  through  the  magnet 
itself.  Every  line  of  magnetic  force  must  have  a  complete  circuit, 


MAGNETISM 


119 


hence,  it  is  impossible  to  have  a  magnet  with  only  one  pole.  Mag- 
netic lines  of  force  complete  their  circuits  independently  and  never 
cut  across  or  merge  into  each  other.  The  fact  that  all  the  lines  of 
force  pass  through  the  magnet  itself  accounts  for  the  concentration 
of  magnetic  force  at  the  poles. 


Fig.  81 — Field  Surrounding  a  Horseshoe  Magnet 

Lines  of  magnetic  force  will  pass  through  some  substances  more 
readily  than  through  others.  When  a  piece  of  iron  is  placed  in  a 
magnetic  field  the  lines  of  force  are  bent  out  of  their  natural  paths 
and  pass  through  the  iron.  There  are  now  more  lines  of  force  passing 
through  the  space  occupied  by  the  iron  than  when  this  space  was 
occupied  by  air  only.  The  property  of  any  substance  for  con- 
ducting magnetic  lines  of  force  is  termed  its  "permeability." 

As  shown  in  Fig.  82  a  bar  of  iron  placed  in  a  magnetic  field  will 
cause  distortion  of  the  lines  of  force,  many  of  which  will  pass  through 


Fig.  82 — Permeabilities  Compared 


120  MOTOR  VEHICLES  AND  THEIR  ENGINES 

the  iron.  Magnetic  lines  of  force  always  take  the  path  of  least  re- 
sistance. If  the  piece  of  iron  is  arranged  free  to  move  in  the  field  it 
will  take  up  such  a  position  as  to  accommodate  through  itself  the 
greatest  possible  number  of  lines  of  force.  If  instead  of  being  a 
magnetic  body  it  is  a  magnet,  it  will  move  under  the  influence  of  the 
magnetic  field  in  which  it  is  placed,  not  only  so  as  to  accommodate 
through  itself  the  lines  of  force  of  the  field  but  also  in  a  particular 
direction  so  that  its  lines  will  be  in  the  same  direction  as  those  of  the 
field.  Thus  a  magnet  always  tends  to  place  itself  so  that  lines  of 
magnetic  force  enter  its  south  pole  and  leave  at  its  north  pole. 

Magnetic  substances  have  the  greatest  permeabilities  but  the 
permeability  of  every  magnetic  substance  is  different.  If  a  piece 
of  steel  is  substituted  for  the  soft  iron  (Fig.  82)  fewer  lines  of  force 
will  pass  through  the  same  space  showing  that  the  conducting  power 
of  iron  is  greater  than  that  of  steel.  The  permeability  of  iron  may 
be  as  high  as  two  thousand  times  that  of  air,  that  is,  two  thousand 
times  as  many  lines  of  force  will  pass  through  the  same  space  when 
occupied  by  iron  as  when  occupied  by  air. 

The  path  taken  by  magnetic  lines  of  force  in  passing  from  any 
pole  of  the  magnet  through  the  surrounding  medium  and  back  to  the 
same  pole  again  is  known  as  a  magnetic  circuit.  The  simple  magnetic 
circuit  is  composed  of  a  magnetic  substance  throughout  its  entire 
length,  as  for  example,  a  magnetized  iron  ring  or  a  horseshoe  magnet 
with  a  keeper  across  its  poles.  A  compound  magnetic  circuit  is  one 
in  which  the  lines  of  force  must  pass  through  both  magnetic  and  non- 
magnetic substances,  as  for  example,  a  horseshoe  magnet  without 
its  keeper. 

If  two  bar  magnets  are  placed  side  by  side  and  the  resultant 
magnetic  field  is  obtained  by  sifting  iron  filings  on  a  paper  covering 


Fig.  83— Field  Resulting  with  Like  Poles  Adjacent 


MAGNETISM 


121 


them.    It  will  be  seen  that  the  arrangement  of  the  lines  of  force  will 
depend  upon  whether  opposite  poles  or  like  poles  are  adjacent. 

When  like  poles  are  adjacent  (Fig.  83)  the  lines  of  force  striking 
against  each  other  are  distorted  from  their  natural  paths  and  com- 
pressed into  a  small  space.  This  causes  the  magnets  to  be  mutually 
repelled  since  the  lines  of  force  try  to  return  to  the  regular  positions 
that  they  normally  occupy. 


Fig.  84 — Field  Resulting  with  Unlike  Poles  Adjacent 

If  unlike  poles  are  adjacent  (Fig.  84)  the  lines  of  force  flowing 
from  the  north  pole  of  each  will  enter  the  adjacent  south  pole  since 
the  steel  offers  a  better  path  than  air  due  to  its  greater  permeability; 
This  causes  the  lines  of  force  to  be  stretched  out  of  their  regular 
positions  and  mutual  attraction  results  since  the  lines  of  force  tend 
to  return  to  their  normal  positions.  Thus  it  is  seen  that  the  like 
poles  of  magnets  repel  while  unlike  poles  attract,  both  of  which  are 
the  direct  result  of  distortion  of  the  magnetic  field. 

It  is  the  same  phenomenon  that  causes  a  piece  of  iron  to  be 
attracted  by  a  magnet.  When  a  piece  of  iron  or  steel  is  near  enough 


Fig.  85 — How  Magnet  Attracts  Iron 


122  MOTOR  VEHICLES  AND  THEIR  ENGINES 

to  a  magnet  to  be  in  its  magnetic  field  the  lines  of  force  stretch  out 
and  pass  through  the  piece  of  iron.  This  causes  a  distortion  of  the 
magnetic  field  and  results  in  the  iron  or  steel  being  drawn  to  the 
nearest  pole  of  the  magnet  (Fig.  85).  While  this  is  taking  place  the 
flow  of  lines  of  force  through  the  piece  of  hpn  or  steel  causes  it  to 
become  a  temporary  magnet.  When  any  body  is  magnetized  by  the 
influence  of  a  magnet  it  is  said  to  be  due  to  magnetic  induction. 
Contact  between  the  inducing  magnet  and  the  body  magnetized  is 
not  necessary  and  may  take  place  through  all  nonmagnetic  substances 
whether  solids,  liquids,  or  gases. 

From  the  foregoing  the  following  laws  of  magnets  have  been 
deduced : 

1.  Unlike  poles  of  magnets  are  mutually  attracted. 

2.  Like  poles  of  magnets  are  mutually  repelled. 

3.  Magnetic  lines  of  force  always  take  the  path  of  least  resistance. 
If  the  polarity  of  a  magnet  is  unknown  it  may  be  tested  by  using 

a  compass  needle  or  other  small  magnet  of  known  polarity  in  ac- 
cordance with  the  laws  just  stated. 

The  molecular  theory  of  magnetism  explains  why  a  piece  of  iron 
or  steel  can  be  magnetized.  All  substances  are  composed  of  minute 
particles  which  are  called  molecules.  The  molecules  composing  iron 
or  steel  are  each  individual  magnets.  When  the  iron  or  steel  is  not 
magnetized  then  the  molecules  arrange  themselves  promiscuously  in 
the  material,  but  according  to  the  law  of  attraction  between  unlike 
poles  local  magnetic  circuits  are  formed  internally  and  there  is  no 
resulting  external  magnetism.  Fig.  86A  illustrates  the  possible 


A  B 

Fig.  86 — Molecules  in  Magnetic  Substance 

positions  in  which  the  particles  composing  a  magnetic  substance  may 
arrange  themselves  when  there  is  no  external  magnetism.  It  must  be 
remembered  that  there  may  be  as  many  as  a  million  or  more  variously 
arranged  magnetic  circuits  in  even  a  very  small  piece  of  iron  or  steel. 
When  the  piece  of  iron  or  steel  is  placed  in  a  magnetic  field  each  little 
magnetized  particle  tends  to  place  itself  so  that  its  axis  is  parallel 
to  the  direction  of  the  magnetic  field  with  its  north  pole  pointing  so 
that  the  lines  of  force  must  pass  out  at  that  end.  This  causes  the 
closed  magnetic  circuits  to  be  broken  up  and  the  particles  to  arrange 
themselves  parallel  to  each  other  with  their  north  poles  all  pointing 
in  the  same  direction  (Fig.  86B).  The  iron  or  steel  now  manifests 


MAGNETISM  123 

external  magnetism  and  will  continue  to  do  so  as  long  as  the  mole- 
cules stay  in  this  arrangement. 

When  under  the  influence  of  a  strong  magnetic  field  soft  iron 
possesses  greater  attractive  force  than  steel.  When  the  magnetic 
field  is  removed,  however,  the  steel  possesses  far  superior  attractive 
properties  to  the  iron  which  it  retains  for  the  most  part  permanently. 
The  soft  iron  is  very  slightly  magnetized  and  what  remains  is  com- 
monly known  as  "  residual  magnetism. "  This  difference  is  easily 
explained  by  the  molecular  theory  of  magnetism.  The  molecules  of 
iron  and  steel  offer  considerable  resistance  to  the  force  tending  to 
turn  them  on  their  axes,  the  resistance  "of  the  steel  molecules  being 
much  greater.  It  is  difficult  to  turn  them  around  but  once  being 
turned  around  it  is  equally  as  difficult  for  them  to  return  to  their 
original  positions  due  to  the  friction  between  themselves,  hence,  the 
resulting  permanent  magnetism  in  steel.  On  the  other  hand  the 
molecules  of  soft  iron  turn  very  readily  when  under  the  influence  of  a 
magnetic  field  but  resume  their  original  positions  when  the  magnetic 
field  is  removed  as  the  friction  between  the  molecules  is  much  less, 
accounting  for  the  temporary  magnetism  in  iron.  Not  all  of  the 
molecules  regain  their  exact  original  positions  which  is  shown  by  the 
slight  trace  of  magnetism  always  found  in  any  piece  of  iron  after 
having  been  magnetized. 

It  is  impossible  to  see  the  molecules  of  iron  or  steel  changing  their 
relative  positions  under  the  influence  of  magnetism  but  by  experiment 
this  theory  has  been  found  to  be  correct.  It  is  assumed  that  the 
molecules  composing  the  iron  or  steel  are  regularly  disposed,  which 
necessarily  has  to  be  the  case.  When  local  magnetic  circuits  are 
formed,  magnetization  turns  the  molecules  on  their  axes  until  they 
are  arranged  symmetrically.  When  they  have  all  been  turned 
around  the  bar  is  said  to  be  saturated  or  completely  magnetized. 
No  matter  how  much  additional  magnetic  force  is  available  the  mag- 
netism of  the  bar  cannot  be  further  influenced. 

Since  magnetism  depends  upon  the  arrangement  of  the  molecules 
in  the  magnetic  substance  their  displacement  will  cause  the  partial 
or  total  loss  of  external  magnetism.  Any  vibration  tends  to  destroy 
permanent  magnetism.  For  this  reason  permanent  steel  magnets 
must  never  be  dropped  or  struck.  Slight  shocks  are  sufficient  to 
demagnetize  soft  iron;  steel  retains  with  tenacity  the  properties  of 
a  magnet  but  its  magnetic  strength  is  impaired  by  shocks  and  will 
be  entirely  destroyed  by  a  sufficient  vibration. 

Vibration  may  be  produced  in  a  substance  by  heat  which  causes 
the  molecules  to  become  more  widely  separated  and  reduces  the 
internal  friction  between  them.  When  sufficient  heat  is  applied  to  a 


124 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


magnet  it  will  entirely  lose  its  magnetism  because  its  molecules  have 
become  disarranged  by  the  resulting  vibration.  For  this  reason  heat 
must  never  be  applied  to  permanent  magnets. 

When  current  flows  through  a  conductor  an  electromagnetic  field 
is  set  up  about  it.  Every  wire  carrying  a  current  possesses  this 
magnetic  field,  which  can  be  proved  by  bringing  a  compass  needle 
near  the  wire.  The  magnetic  field  of  the  wire  acts  on  the  magnetic 
field  of  the  compass  needle  causing  it  to  be  deflected.  If  a  wire 
through  which  current  is  flowing  is  passed  through  paper  upon  which 
iron  filings  are  sifted  they  will  arrange  themselves  in  concentric 


Fig.  87 — Field  About  Current  Carrying  Conductor 

circles  with  the  wire  at  the  center  as  shown  in  Fig.  87.  Thus,  it  is 
seen  that  the  magnetic  field  around  a  straight  wire  carrying  a  current 
consists  of  a  cylindrical  whirl  of  circular  lines,  their  intensity  decreas- 
ing as  the  distance  from  the  wire  increases  as  shown  in  Fig.  88.  As  is 
true  of  all  lines  of  magnetic  force  these  magnetic  whirls  do  not 
merge,  cross,  or  cut  each  other,  but  complete  their  circuits  independ- 
ently around  the  wire. 

The  direction  of  the  magnetic  whirls  about  the  wire  depends  upon 
the  direction  the  current  is  flowing  through  it.  If  the  thumb  of  the 
right  hand  is  placed  along  the  wire  in  the  direction  in  which  the  cur- 
rent is  flowing  the  curved  fingers  will  indicate  the  direction  of  the 
magnetic  whirls  about  the  wire.  This  may  be  checked  by  placing 
a  compass  needle  near  the  wire  which  will  show  the  direction  of  the 
lines  of  force  by  its  deflection. 


Fig.  88—- Magnetic  Whirls 


MAGNETISM 


125 


If  a  wire  is  arranged  as  shown  in  Fig.  89  so  that  it  describes  a 
half  circle  above  the  cardboard  its  magnetic  field  will  be  shown  by 

sifting  iron  filings  on  the 
cardboard.  When  current  is 
passing  through  the  wire  the 
iron  filings  arrange  themselves 
circularly  around  the  wire. 
It  is  seen  that  the  magnetic 
lines  of  force  pass  down 
through  the  center  of  the 
loop,  which  can  be  confirmed 
by  applying  the  right  hand 


Fig.  89— Direction  of  Field  Through 
Loop  of  Wire 


rule. 


If  a  wire  is  bent  into  a  circular  loop  and  current  sent  through  it 
(Fig.  90)  all  the  magnetic  whirls  about  the  wire  will  pass  in  through 

one  side  of  the  loop  and  out 
the  other.  If  a  compass  needle 
is  brought  near  the  loop  it 
will  be  attracted  by  the  mag- 
netic field  of  the  loop  just  as  it 
would  be  by  a  bar  magnet. 
This  is  due  to  the  fact  that 
the  side  of  the  loop  from 
which  the  magnetic  whirls 
emerge  acts  as  the  north  pole 
while  the  other  side  manifests 
south  polarity. 

If  a  coil  of  wire  is  wound 
into  a  helix  and  current  sent 
Fig.  90 — Whirls  About  Loop  of  Wire     through  it,  the  result  will  be  as 

shown  in  Fig.  91.     Magnetic 

whirls  are  set  up  about  each  turn  of  the  helix  but  the  turns  of  wire 
being  so  near  each  other,  the  whirls  instead  of  completing  separate 


Fig.  91— Field  About  Helix 

circuits  join  together  looping  all  the  turns  composing  the   helix 
resulting  in  a  continuous  magnetic  field.     The  total  field  is  the 


126  MOTOR  VEHICLES  AND  THEIR  ENGINES 

sum  of  the  magnetic  lines  of  each  individual  turn,  since  it  is  the 
result  of  the  whirls  about  adjacent  conductors  joining  together  and 
the  sum  of  all  the  turns  constitutes  the  field  or  total  number  of 
lines  of  force  passing  through  the  coil.  The  field  set  up  by  the  coil 
is  shown  in  Fig.  91  and  it  will  be  seen  that  one  end  of  the  coil  is  the 
north  pole  while  the  other  end  is  the  south  pole,  just  as  was  true  of 
the  two  sides  of  the  single  loop  of  wire  through  which  current  was 
flowing.  If  the  curved  fingers  of  the  right  hand  are  placed  about 
the  coil  of  wire  in  the  direction  the  current  is  flowing  the  thumb 
will  indicate  the  north  pole  of  the  coil. 

When  a  great  many  turns  of  wire  are  wound  on  a  wooden  or  brass 
spool  similar  to  the  winding  of  a  spool  of  thread  the  resulting  coil  is 
called  a  "solenoid." 

An  iron  or  steel  bar  inserted  in  a  solenoid  through  which  current 
is  flowing  is  a  much  better  conductor  of  the  magnetic  lines  of  force 
inside  the  solenoid  than  the  air,  so  that  the  strength  or  attractive 
force  of  the  solenoid  is  materially  increased  though  the  magnetizing 


Fig.  92 — Electro-Magnet 

current  is  the  same  as  before.  An  iron  core  introduced  into  a  sole- 
noid carrying  a  current  becomes  strongly  magnetized  and  is  called 
an  electro-magnet  (Fig.  92).  The  direction  of  the  lines  of  force 
through  the  iron  core  of  the  solenoid  is  the  same  as  their  natural 
direction  through  the  solenoid  alone  so  that  the  laws  of  polarity  of 
the  solenoid  hold  for  the  electro-magnet.  The  molecular  theory  of 
magnetism  explains  how  magnetism  is  produced  in  the  iron  bar  by 
passing  current  around  it.  The  solenoid's  magnetic  field  acts  upon 
the  molecules  composing  the  iron  bar  causing  them  to  arrange  them- 
selves producing  an  external  field  about  the  core.  The  magnetic 
field  set  up  by  the  current  simply  makes  evident  the  latent  magne- 
tism of  the  iron.  This  molecular  action  also  accounts  for  the  per- 
manent magnetism  produced  in  a  piece  of  steel,  inserted  in  a  solenoid 


MAGNETISM  127 

after  the  current  ceases,  since  the  friction  between  the  molecules 
prevents  many  of  them  resuming  their  original  positions. 

If  a  coil  of  wire  is  wound  around  an  iron  ring,  and  current  sent 
through  it,  lines  of  magnetic  force  will  flow  around  through  the  iron 
ring.  If  a  small  air  gap  is  made  in  the  ring  by  sawing  out  a  section 
a  compound  circuit  is  formed  and  lines  of  force  are  compelled  to 
pass  through  the  air  gap  to  complete  their  circuit  so  that  north  and 
south  poles  are  produced.  The  lines  of  force  through  the  iron  part 
of  the  circuit  are  not  nearly  so  dense  as  before,  since  the  resistance  of 
the  circuit  has  been  increased  by  introducing  an  air  gap.  If  the 
removed  section  of  the  ring  is  now  replaced  and  the  ring  covered  with 
iron  filings,  while  it  is  magnetized,  a  great  many  filings  will  be  attracted 
at  the  two  joints.  This  illustrates  magnetic  leakage.  When  mag- 
netic leakage  takes  place  with  permanent  magnets  their  strength  is 
impaired.  This  should  be  guarded  against  especially  when  dis- 
mounting the  magnets  of  magnetos. 


CHAPTER  XIII 


ELEMENTARY  ELECTRICITY 

The  term  electricity  has  been  applied  to  an  invisible  force  known 
only  by  the  effects  it  produces.  Its  exact  nature  is  not  known  but 
the  laws  governing  it  are  clearly  understood  and  defined.  These 
can  best  be  explained  by  comparing  its  flow  to  that  of  water  to  which 
it  is  similar.  However,  it  must  be  remembered  that  electricity  is 
not  a  liquid  and  is  only  compared  to  water  to  better  understand  its 
flow. 


Fig.  93 — Water  Analogy  to  Flow  of  Current 

Fig.  93  shows  two  tanks  "A"  and  "B"  at  the  same  level  ("A" 
being  filled  with  water)  connected  by  a  pipe  in  which  is  placed  a 
valve.  When  the  valve  is  opened  slightly  the  water  will  flow  from 
"A"  into  "B"  until  the  level  of  water  in  both  tanks  is  the  same. 
If  the  valve  had  been  opened  wider,  the  flow  of  water  would  have 
been  faster  because  the  larger  opening  offers  less  resistance  to  its 
flow.  Had  air  been  pumped  into  the  top  of  tank  "A"  until  a  high 
pressure  was  obtained  the  flow  of  water  through  the  pipe  into  tank 
"B"  would  have  been  still  faster.  Although  the  rate  at  which  the 
water  flows  from  tank  "A"  into  tank  "B"  may  vary,  the  quantity 
that  flows  is  independent  of  the  rate  and  depends  only  upon  the 
difference  in  pressure  between  the  two  tanks.  It  is  seen  that  pressure 
is  required  to  cause  water  to  flow  and  the  rate  of  flow  may  be  in- 
creased by  reducing  the  resistance  to  its  passage  or  by  increasing  the 
pressure. 

In  Fig.  94  the  two  terminals  "A"  and  "B"  of  the  dry  cell  are 
connected  by  a  wire  through  the  switch  "C."  This  may  be  com- 
pared to  the  two  tanks  connected  by  a  pipe;  the  positive  terminal 

128 


ELEMENTARY  ELECTRICITY 


129 


"A"  corresponding  to  the  full  tank,  the  negative  terminal  "B" 
corresponding  to  the  empty  tank,  the  wire  to  the  pipe,  and  the  switch 

"C"  to  the  valve.  When  the 
switch  is  closed  current  flows 
from  "A"  to  "B"  through  the 
wire.  The  water  flows  from 
tank  "A"  to  tank  "B"  be- 
cause there  is  greater  pressure 
at  "A"  than  at  "B."  Current 
flows  from  terminal  "A"  to 
terminal  "B"  because  there  is 
greater  electrical  pressure  at 
"A"  than  at  "B." 

Water  pressure  is  usually 
measured  in  pounds  per  square 
inch,  electrical  pressure  is  meas- 
ured in  volts.  The  amount  of 
water  that  flows  may  be  meas- 


Fig.   94 — Simple  Electric  Circuit 


ured  in  gallons  or  barrels,  the  amount  of  current  that  flows  is 
measured  in  amperes.  The  smaller  or  longer  the  pipe  the  less  will 
be  the  water  flowing  through  it  due  to  the  increased  resistance; 
similarly,  the  smaller  or  longer  the  wire  the  less  will  be  the 
current  flowing  through  it  due  to  the  increased  resistance  and  this 
electrical  resistance  is  measured  in  ohms. 

The  pound  and  the  gallon  are  definite  units  of  pressure  and  quan- 
tity both  of  which  are  familiar  due  to  their  common  usage.  Years 
ago  in  order  to  decide  upon  similar  units  for  measuring  electricity  a 
committee  was  appointed  made  up  of  prominent  scientists  of  the 
time.  Dr.  Ohm  was  chairman  of  this  committee  which  met  in  his 
laboratory  to  decide  the  units  by  which  electrical  pressure,  current, 
and  resistance  should  be  measured. 

It  was  decided  that  the  amount  of  pressure  given  by  a  certain  cell 
should  be  the  standard  unit  to  which  all  other  electrical  pressure 
should  be  compared.  The  cell  chosen  was  the  Voltaic  Cell  and  the 
amount  of  pressure  this  cell  gave  was  named  the  "Volt."  A  six  volt 
battery  is  one  having  six  times  the  pressure  of  the  Voltaic  cell. 

To  obtain  the  unit  of  resistance  it  was  decided  to  take  a  certain 
conductor  and  call  its  resistance  the  standard  to  which  all  others 
should  be  compared.  The  one  chosen  was  a  tube  of  mercury  of 
definite  size  and  length  and  the  amount  of  its  resistance  to  the  flow 
of  current  through  it  was  named  the  "Ohm."  A  conductor  which 
has  three  ohms  resistance  is  one  that  offers  three  times  as  much  resist- 
ance to  the  flow  of  current  as  the  original  tube  of  mercury. 


130  MOTOR  VEHICLES  AND  THEIR  ENGINES 

To  obtain  the  unit  of  current  it  was  decided  to  take  this  cell 
giving  one  volt  pressure  and  connect  its  terminals  with  the  tube  of 
mercury  and  the  amount  of  current  that  flowed  was  named  the 
"  Ampere."  A  circuit  which  has  10  amperes  flowing  through  it  is 
one  in  which  the  current  is  10  times  as  great  as  that  caused  to  flow 
by  a  pressure  of  one  volt  through  one  ohm  resistance. 

Referring  to  Fig.  93  if  the  pressure  is  increased  and  the  pipe  size 
and  length  remains  the  same  more  water  will  flow;  the  same  is  true 
of  electricity.  If  the  pressure  (voltage)  is  increased,  more  current 
(amperes)  will  flow  through  the  circuit  provided  the  resistance  is 
not  changed.  If  the  pressure  remains  the  same  but  the  size  of  the 
valve  opening  is  made  smaller  or  the  pipe  decreased  in  size  or  in- 
creased in  length,  less  water  will  flow;  the  same  is  true  in  electric 
circuits.  If  the  pressure  (voltage)  remains  the  same  and  the  wire  is 
decreased  in  size  or  increased  in  length,  increasing  the  resistance 
(ohms),  less  current  (amperes)  will  flow. 

By  experiment  it  has  been  found  that  the  flow  of  electricity 
always  depends  upon  the  pressure  and  resistance  of  the  circuit  and 
that  definite  laws  govern  the  amount  of  change  in  the  flow  of  elec- 
tricity for  a  given  change  of  either  of  these.  The  relation  between 
electrical  pressure,  current,  and  resistance  is  known  as  Ohm's  Law 
and  is  as  follows : 

First:  The  strength  of  current  flowing  in  any  circuit  is  equal  to 
the  pressure  in  volts  divided  by  the  resistance  of  the  circuit  in  ohms. 

Second:  The  strength  of  current  in  any  circuit  increases  or 
decreases  directly  as  the  pressure  increases  or  decreases  when  the 
resistance  is  constant.  With  a  constant  pressure  the  current  in- 
creases as  the  resistance  is  decreased  and  decreases  as  the  resistance 
is  increased. 

n  Pressure 

Current    =  

Resistance 

Volts 


Amperes  = 


Ohms 
R~ 


Problem  1. 

With  a  six-volt  battery  and  a  circuit  of  two  ohms  resistance,  how 
many  amperes  of  current  will  flow  in  the  circuit? 

T       E         6         Q 

I  =  — =  —     =3  amperes. 

R         2 

Problem  2. 

If  the  voltage  is  increased  to  12  volts  and  the  resistance  is  the 
same,  how  many  amperes  of  current  will  flow? 


ELEMENTARY  ELECTRICITY  131 


T       E      12 

I  =  — = —  =  6  amperes. 

This  proves  that  as  the  voltage  increases,  the  current  increases. 

Problem  3. 

If  the  resistance  is  increased  to  3  ohms  and  the  voltage  is  the  same, 
how  many  amperes  of  current  will  flow? 

E       6 

I  =  —  =  —  =  2  amperes. 
R       3 

This  proves  that  as  the  resistance  is  increased  the  current  is  decreased. 

If  the  two  tanks  "A"  and  "B"  (Fig.  93)  are  connected  by  a 
solid  rod,  no  water  can  flow,  a  hollow  rod  or  pipe  is  necessary  to  permit 
water  to  pass  through  it.  If  the  terminals  "A"  and  "B"  (Fig.  94)  of 
the  dry  cell  were  connected  by  a  glass  rod  no  current  could  flow,  a  met- 
al rod  or  wire  is  necessary  to  permit  electric  current  to  pass  through  it. 
For  this  reason  metals  and  other  substances  that  electricity  flows 
through  easily,  due  to  their  low  resistance,  are  called  CONDUCTORS. 

To  retain  water,  a  pipe  must  be  made  of  strong  enough  material 
to  withstand  the  pressure  exerted  by  the  water  passing  through  it. 
Similarly,  to  retain  the  current  passing  through  it  a  wire  must  be 
surrounded  by  some  material  through  which  current  cannot  pass. 
Materials  which  offer  considerable  resistance  to  the  passage  of  cur- 
rent through  them  are  called  non-conductors  or  INSULATORS. 

All  conductors  do  not  conduct  electricity  equally  well  since  the 
resistance  of  every  substance  is  different.  Silver,  copper,  aluminum, 
steel,  and  iron  are  all  good  conductors  and  offer  but  little  resistance 
to  the  flow  of  current.  Materials  such  as  glass,  porcelain,  rubber, 
silk,  cotton,  fiber,  wood,  and  air  offer  a  great  deal  of  resistance  to 
the  flow  of  current  and  are  classed  as  insulators.  As  in  the  case  of 
conductors,  all  insulators  do  not  resist  the  flow  of  current  equally 
well. 

Ohm's  Law  proves  that  the  pressure  in  an  electric  circuit  deter- 
mines the  amount  of  current  that  will  flow.  In  other  words  pressure 
can  overcome  resistance  and  force  current  to  flow.  For  this  reason 
when  the  pressure  is  high  in  a  circuit  an  insulator  of  much  higher 
resistance  must  be  used  than  would  be  necessary  if  the  pressure 
were  low. 

For  electric  current  to  flow  a  path  consisting  of  conductors  must 
be  provided.  A  break  in  the  circuit  will  cause  the  current  to  cease 
flowing  and  it  is  said  to  be  "open  circuited." 

The  common  circuits  used  in  ignition,  lighting,  and  starting  work 
are  series  and  parallel. 


132 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


SERIES  CIRCUIT :    When  electric  lamps  are  connected  as  shown 
i  n  Fig.  95  they  are  said  to  be  in  series  because  the  current  flows  through 


0-0-On 

LAMPS 


Fig.  95 — Series  Circuit 

each  lamp  to  the  next  succeeding  one,  returning  from  the  last  one 
to  the  battery.  In  a  circuit  of  this  kind  the  resistance  increases  as 
the  number  of  lamps  is  increased,  decreasing  the  current  if  the 
pressure  remains  the  same. 


O 


2S477Z7BK 


LAMPS 


Fig.  96— Parallel  Circuit 

PARALLEL  CIRCUITS.— When  electric  lamps  are  connected  as 
shown  in  Fig.  96  they  are  said  to  be  connected  in  parallel.     All  the 


Fig.  97— Water  Analogy  to  Parallel  Circuit 


ELEMENTARY  ELECTRICITY  133 

• 

current  in  this  case  does  not  have  to  flow  through  every  lamp  but 
part  of  it  flows  through  each  and  back  to  the  battery  through  the 
common  return  wire. 

If  two  tanks  "A"  and  "B"  are  connected  as  shown  in  Fig.  97 
and  valve  "C"  is  opened,  a  certain  amount  of  water  will  flow  between 
them.  If  valve  "D"  is  opened  more  water  will  flow  because  another 
path  has  been  opened,  reducing  the  total  resistance.  If  valve  "E" 
is  opened  a  still  greater  quantity  of  water  will  flow. 

This  is  the  same  arrangement  as  shown  in  Fig.  96  and  as  more 
lamps  are  added  the  total  resistance  of  the  circuit  is  reduced  and  more 
current  flows  if  the  pressure  remains  the  same. 

Lights  on  cars  are  usually  connected  in  parallel  since  turning  on 
additional  lights  will  not  require  a  change  of  voltage.  Also,  the 
burning  out  of  one  light  will  not  put  out  any  of  the  others. 

In  making  up  wiring  diagrams  certain  electrical  symbols  are  used. 
Fig.  98  shows  those  adopted  by  common  usage. 


£LCCTft/CAL      SYMBOLS 

US£0  /Af    Hf/MAfff  0/A6/tAMS 

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Fig.  98 

134 


CHAPTER  XIV 


Fig.  99— Simple  Cell 


BATTERIES 

The  simplest  method  of  producing  electric  current  is  by  chemical 
means.  A  simple  primary  cell  may  be  made  by  placing  two  dis- 
similar metals  in  an  acid  or  alkaline  solution.  Fig.  99  shows  a  plate 
of  zinc  and  a  plate  of  copper 
placed  in  a  glass  jar  containing 
a  solution  of  sulphuric  acid.  If 
the  plates  are  connected  by  a 
piece  of  wire  a  chemical  reaction 
takes  place  between  the  zinc 
plate  and  the  acid  causing  the 
zinc  to  be  gradually  wasted 
away.  This  causes  the  terminal 
at  the  copper  plate  to  be  posi- 
tively charged,  resulting  in  a 
flow  of  current  from  the  termi- 
nal at  the  copper  plate  through 
the  wire  to  the  terminal  at  the 
zinc  plate.  This  action  will 
continue  as  long  as  any  of  the  zinc  is  left  or  until  the  acid  has  become 
so  weak  that  its  power  to  attack  the  zinc  is  exhausted.  If  the  con- 
nection between  the  plates  is  broken  at  any  time  the  chemical 
reaction  stops  and  will  only  continue  when  the  circuit  is  again  made. 
This  is  the  simplest  form  of  chemical  cell  and  illustrates  the  funda- 
mental principle  underlying  the  operation  of  all  chemically  produced 
electric  current. 

There  are  many  kinds  of  cells  for  chemically  producing  electric 
current  but  there  are  only  two  which  are  applicable  for  ignition  on 
motor-propelled  vehicles.  These  are  the  Dry  Cell  and  Storage  Cell 
and  are  the  only  types  which  will  be  discussed  in  this  chapter. 

DRY  CELL. — The  active  elements  of  the  dry  cell  consists  of  a 
zinc  shell  "1"  in  the  center  of  which  a  carbon  rod  "3"  is  placed 
(Fig.  100).  Next  to  the  zinc  shell  is  placed  blotting  paper  "2" 
which  is  soaked  with  the  active  chemical  (usually  salamoniac  or 
zinc  chloride)  called  the  electrolyte.  The  carbon  rod  is  surrounded 
by  some  depolarizing  material  (usually  manganese  dioxide)  and  the 
space  between  is  filled  with  a  compound  "4"  usually  kept  secret  by 

135 


136 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


the  manufacturer.    To  make  the  cell  watertight  it  is  sealed  at  the 

top  with  pitch  "5." 

The  zinc  shell  is  attacked  by  the  active  chemical  and  is  eaten 

away.     During  this  chemical  action  hydrogen  gas  is  liberated  and  I 

collects  on  the  carbon  rod  in  small 
bubbles.  These  would  insulate  it  if  it 
were  not  for  the  action  of  the  depolari- 
zer which  combines  with  the  hydrogen 
to  form  water.  The  voltage  of  a  dry 
cell  of  the  kind  just  described  is  ap- 
proximately \y^  volts  on  open  circuit 
when  new  and  in  good  condition 
irrespective  of  the  size  of  the  cell.  A 
large  cell  of  the  same  construction  will 
give  more  current  than  a  small  one  but 
the  voltage  will  not  be  increased.  The 
ordinary  size  of  dry  cell  will  giva  20  to 
35  amperes  of  current  when  the  circuit 
is  first  closed.  The  cell  will  deliver  this 
maximum  amount  of  current  for  only  a 
very  short  length  of  time.  For  this 
reason  dry  cells  are  only  suitable  for 
intermittent  circuits. 

A  battery  consists  of  two  or  more 
cells  which  are  connected  together  to 
obtain  suitable  voltage  and  current. 
The  arrangement  or  connection  will 
depend  upon  the  requirements  of  the 

circuit  for  which  the  battery  is  to  supply  current. 

There  are  three  methods  of  connecting  dry  cell  to  form  batteries; 

series,  parallel,  and  series-parallel. 


Fig.  100 — Cross-Section 
Through  Dry  Cell 


Fig.  101— Cells  in  Series 

Fig.  101  shows  a  battery  composed  of  dry  cells  connected  in  series. 
The  positive  terminal  of  one  cell  is  connected  to  the  negative  of  the 
next  succeeding  cell  and  the  line  is  connected  to  the  remaining 


BATTERIES 


137 


terminals.  When  cells  are  connected  in  series  the  voltage  of  the 
battery  is  equal  to  the  sum  of  the  voltages  of  all  the  cells.  That  is,  the 
voltage  of  a  battery  is  the  voltage  of  one  cell  times  the  number  of 
cells  when  each  cell  has  the  same  voltage.  The  amperage  of  the 
battery  will  be  equal  to  the  amperage  of  one  cell.  For  example,  if 
each  cell  in  Fig.  101  has  a  strength  of  1J^  volts  and  25  amperes,  the 
strength  of  the  battery  will  be  9  volts  and  25  amperes. 


Fig.  102— Cells  in  Parallel 

Fig.  102  shows  a  battery  of  dry  cells  connected  in  paraUel.  The 
positive  terminals  of  all  the  cells  are  connected  to  one  line  and  all  the 
negative  terminals  to  the  other  line.  When  cells  are  connected  in 
parallel  it  is  necessary  that  every  cell  be  of  the  same  voltage.  The 
voltage  of  the  battery  will  be  equal  to  the  voltage  of  one  cell.  The 
amperage  will  be  equal  to  the  sum  of  the  amperes  of  all  the  cells. 
That  is  the  amperage  of  the  battery  is  equal  to  the  amperage  of  one 
cell  times  the  number  of  cells  when  the  amperage  of  each  cell  is  the 
same.  For  example,  if  the  cells  in  Fig.  102  are  each  of  1J^  volts  and 
25  amperes  the  strength  of  the  battery  will  be  1J^  volts  and  150 
amperes. 

These  two  methods  of  connecting  cells  to  form  batteries  are  the 
most  common;  however,  when  increased  voltage  and  amperage  are 
both  desired  the  cells  must  be 
connected  in  series-parallels. 

Fig.  103  shows  a  battery  of 
dry  cells  connected  in  series- 
parallel.  It  is  made  up  of  sets 
of  cells  connected  in  series,  each 
of  these  sets  being  connected  in 
parallel.  The  voltage  of  this 
battery  is  equal  to  that  of  each 
set  of  cells  connected  in  series. 
The  amperage  is  equal  to  the 
sum  of  the  amperes  delivered 
by  each  set.  For  example,  if 
the  cells  in  Fig.  103  are  each  of  Fig.  103— Cells  in  Series-Parallel 


138 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


volts  and  25  amperes  the  strength  of  each  set  in  series  will  be 
6  volts  and  25  amperes.  The  strength  of  the  battery  will  therefore 
be  6  volts  and  100  amperes. 

STORAGE  BATTERIES.— These  batteries  are  almost  without 
exception  the  only  kind  used  on  modern  motor-propelled  vehicles. 
The  reason  for  this  is  the  adoption  of  starting  and  lighting  systems 
as  standard  equipment  on  most  motor  vehicles. 

In  the  storage  cell  the  current  results  from  chemical  action  the 
same  as  in  the  simple  primary  cell.  The  plates  or  electrodes  are 
usually  built  upon  grids  which  are  perforated  as  shown  in  Fig.  104. 

The  group  of  plates  connected  to 
the  positive  terminal  of  the  cell 
consists  of  grids  filled  with  a  paste 
of  lead  peroxide  characterized  by  its 
brown  color.  The  group  of  plates 
connected  to  the  negative  terminal 
of  the  cell  consists  of  grids  filled 
with  metallic  lead  of  a  spongy 
nature  and  is  dull  gray  in  color. 
These  plates  are  arranged  in  the 
cell  so  that  the  positive  and  the 
negative  plates  alternate.  Between 
the  plates  are  placed  separators 
which  are  to  prevent  the  plates  of 
the  positive  and  negative  groups 
from  coming  in  contact.  The 
separators  must  be  porous  to  allow 
the  solution  to  pass  through  freely 
and  are  usually  made  of  specially  treated  wood  or  hard  rubber. 
The  jar  or  container  in  which  the  plates  are  placed  is  usually  made  of 
hard  rubber  which  is  not  affected  by  the  acid.  The  assembly  of 
plates  and  separators  (Fig.  105)  is  placed  in  this  jar  or  container  and 
a  solution  of  sulphuric  acid  and  distilled  water  is  added  until  the  level 
of  the  liquid  in  the  jar  covers  the  tops  of  the  plates.  The  cell  is 
sealed  by  a  cover  of  hard  rubber  through  which  the  positive  and 
negative  terminals  project  (Fig.  106).  A  filler  cup  is  provided 
through  which  an  air  vent  is  left  for  the  escape  of  gas  which  may  be 
formed  in  the  cell. 

Storage  cells  are  connected  in  series  to  form  batteries  which  will 
give  higher  voltage.  The  voltage  of  a  storage  cell  is  usually  con- 
sidered two  volts  since  this  is  the  average  value.  If  greater  amperage 
is  desired  the  size  of  the  cell  is  increased.  The  rating  of  storage 
batteries  is  usually  given  in  volts  and  ampere  hours.  Ampere 


*«S8|lip| 


Fig.  104— Grid 


BATTERIES 


139 


Fig.  105— Plate  Assembly 


UNSCREW 
THIS  CAP 


Fig.  106 — Cross-Section  Through  Storage  Cell 


140  MOTOR  VEHICLES  AND  THEIR  ENGINES 

hours  means  that  if  the  battery  is  discharged  at  a  certain  definite 
rate  it  will  give  a  certain  current  for  so  many  hours.  If  10  amperes 
was  the  rate  of  discharge  upon  which  it  was  rated,  a  6  volt  120  ampere- 
hour  battery  would  be  one  having  3  cells  connected  in  series  and  would 
give  10  amperes  of  current  for  12  hours.  If  the  battery  was  dis- 
charged at  a  high  rate,  20  amperes,  it  would  not  last  for  6  hours  and 
likewise  if  discharged  at  a  low  rate,  5  amperes,  it  would  usually  last 
much  longer  than  24  hours.  Therefore,  the  ampere-hour  life  of  a 
battery  is  governed  by  the  rate  at  which  it  is  discharged. 

When  a  storage  battery  is  discharging  a  chemical  reaction  takes 
place.  The  sulphuric  acid  (H2S04)  is  broken  up  into  two  parts,  H2 
and  SC>4.  The  hydrogen  is  liberated  at  the  lead  peroxide  plates 
(Pb02)  reducing  them  to  lead  oxide  (PbO)  which  combines  with 
part  of  the  sulphuric  acid  to  form  lead  sulphate  (PbSO^  and  water 
(H20).  The  SC>4  is  liberated  at  the  spongy  lead  plates  (Pb)  and 
combines  with  them  to  form  lead  sulphate  (PbS04).  During  this 
process  the  electrolyte  grows  less  concentrated  because  of  the  ab- 
sorption of  S(>4  by  the  spongy  lead  plates. 

When  the  battery  is  being  charged  by  passing  current  through  it 
in  the  opposite  direction  the  chemical  action  just  described  is  re- 
versed. The  lead  sulphate  on  one  plate  is  converted  back  to  lead 
peroxide,  the  lead  sulphate  on  the  other  plate  is  reduced  to  spongy 
lead,  and  the  electrolyte  becomes  more  dense  due  to  the  increased 
amount  of  sulphuric  acid.  The  following  is  the  chemical  reaction 
which  takes  place  in  a  storage  cell  while  discharging  and  being 
charged. 

DISCHARGING 

Positive   plate  Pb02  +  H2  +  H2S04  =  PbS04  +  2  H20 

t 

Negative  plate  Pb    +    S04  =  PbS04 

CHARGING 

Positive   plate  PbS04+0    +    H20     =    Pb02    +    H2S04 

I 

Negative  plate  PbS04+H2  =    Pb      -f      H2S04 

The  current  in  a  storage  cell  results  from  chemical  action  just  as 
in  any  other  cell.  When  a  dry  cell  is  exhausted  it  is  thrown  away 
while  the  storage  cell  is  restored  to  normal  condition  by  passing  direct 
current  through  it  from  some  outside  source.  By  this  process  the 
chemical  reaction  which  took  place  upon  discharge  is  reversed 
restoring  the  elements  to  their  original  condition.  It  is  erroneous 
to  say  that  electricity  is  stored  in  a  storage  cell.  The  storage  cell  is 


BATTERIES 


141 


noo 


7200 


a  means  of  converting  electrical  energy  into  chemical  energy  during 
charge  and  chemical  energy  into  electrical  energy  during  discharge. 

During  discharge  some  of  the  sulphuric  acid  combines  with  the 
plates  causing  the  solution  to  have  a  greater  proportion  of  water 
to  sulphuric  acid,  this  proportion  increasing  as  the  discharg- 
ing continues.  The  relative 
amounts  of  acid  and  water  can 
be  determined  by  reading  the 
specific  gravity  of  the  solution. 
This  is  accomplished  by  the  use 
of  an  instrument  called  a  hydro- 
meter contained  in  a  syringe 
(Fig.  107).  The  electrolyte  is 
drawn  up  into  the  syringe  by 
the  bulb  and  the  hydrometer 
will  sink  to  a  greater  or  less 
amount  depending  upon  the 
amount  of  sulphuric  acid  in  the 
solution.  If  the  hydrometer 
reads  1.280  it  indicates  that  the 
liquid  is  1.280  times  as  heavy  as 
water.  The  scale  of  the  hydro- 
meter is  read  on  the  stem  at  the 
surface  of  the  liquid  when  the 
hydrometer  is  floating  in  it 
(Fig.  107). 

The  readings  of  the  hydrometer  shows  the  condition  of  the  battery 
in  accordance  with  the  following  table: 


Fig.  107 — Hydrometer  and  Syringe 


READING 

1.280-1.300 

1.250 

1.215 

1.180 

1.150 


CONDITION 
Full  charge 
34  Discharged 
J/£  Discharged 
%  Discharged 
Discharged 


During  the  chemical  reaction  which  takes  place  in  charge  and 
discharge  heat  is  generated  and  causes  the  loss  of  some  of  the  water 
but  there  is  no  loss  of  sulphuric  acid.  For  this  reason  when  the  solu- 
tion in  the  cells  gets  below  the  top  of  the  plates  more  distilled  water 
must  be  added.  When  adding  distilled  water  care  must  be  taken 
not  to  fill  the  cell  full.  This  is  apt  to  result  in  the  loss  of  some  of  the 
solution  through  the  vent,  the  acid  attacking  the  metal  parts  causing 


142  MOTOR  VEHICLES  AND  THEIR  ENGINES 

them  to  become  corroded  and  eaten  away.  If  acid  is  spilled  or  slops 
out  on  the  battery  box  it  will  soon  be  destroyed.  In  addition  to 
this  if  some  of  the  solution  is  spilled  there  is  no  way  to  determine 
how  much  acid  has  been  lost  and  it  cannot  be  replaced  with  certainty. 

Never  take  readings  of  the  specific  gravity  of  a  cell  immediately 
after  adding  water  to  a  cell.  When  taking  a  hydrometer  reading  with 
a  syringe  be  sure  to  return  the  solution  to  the  same  cell  from  which 
it  was  taken.  Under  no  circumstances  should  acid  of  any  kind  be 
added  to  a  cell  which  has  once  been  put  in  operation. 

When  a  bettery  is  to  be  prepared  for  service  remove  the  black 
hard  rubber  vents  which  are  standard  equipment  and  remain  on  the 
battery  when  in  service.  The  cells  should  be  filled  to  the  bottom  of 
the  vent  holes  with  1.275  specific  gravity  electrolyte  at  70  degrees 
Fahrenheit.  1.275  specific  gravity  electrolyte  consists  of  approx- 
imately two  and  one-half  parts  by  volume  of  distilled  water  and  one 
part  by  volume  of  chemically  pure  sulphuric  acid.  The  acid  should 
be  poured  into  the  water  and  allowed  to  cool  below  90  degrees 
Fahrenheit  before  being  used.  Never  fill  the  battery  with  electrolyte 
above  90  degrees  Fahrenheit. 

Allow  the  battery  to  stand  for  twelve  hours  and  add  more  1.275 
specific  gravity  acid  if  necessary  to  bring  the  level  up  to  the  bottom 
of  vent  holes.  Then  start  charging  at  the  finish  rate  stamped  on  the 
name  plate  for  not  less  than  72  hours  or  until  the  specific  gravity 
of  the  electrolyte  stops  rising.  At  the  end  of  charge  each  cell 
should  be  gassing  freely  and  the  voltage  should  read  at  least  2.4 
volts  per  cell. 

While  charging  add  distilled  water  to  replace  any  electrolyte  lost 
by  evaporation.  If  during  the  charge  the  temperature  in  any  one 
cell  exceeds  110  degrees  Fahrenheit  the  current  must  be  reduced 
until  the  temperature  falls  below  100  degrees  Fahrenheit.  This 
will  necessitate  a  longer  time  to  complete  the  charge,  but  must  be 
strictly  adhered  to. 

The  batteries  are  now  completely  charged  and  the  specific  gravity 
of  the  electrolyte  should  be  between  1.290  and  1.310  in  each  cell. 
If  above  1.310  remove  a  little  electrolyte  and  add  the  same  amount  of 
distilled  water  while  the  battery  is  left  charging  (in  order  to  thor- 
oughly mix  the  solution)  and  after  three  hours  if  the  electrolyte  is 
within  the  limits,  the  cell  is  ready  for  service.  If  the  specific  gravity 
is  below  1.290  remove  a  little  electrolyte  and  add  the  same  amount 
of  1.400  specific  gravity  electrolyte  and  leave  on  charge  as  before 
1.400  specific  gravity  electrolyte  consists  of  seven  parts  chemically 
pure  sulphuric  acid  and  nine  parts  distilled  water  by  volume.  The 
acid  should  be  poured  into  the  water  and  allowed  to  cool  below  90 


BATTERIES  143 

degrees  Fahrenheit  before  being  used.  The  standard  vent  plugs  are 
now  inserted  and  the  battery  is  ready  for  service. 

A  storage  battery  requires  constant  care  and  attention  and  if 
treated  properly  will  give  most  satisfactory  service  but  if  neglected 
will  cause  constant  trouble  and  soon  become  unserviceable.  A 
battery  should  be  held  rigid  in  the  battery  box  to  prevent  spilling  of 
the  solution.  There  should  be  an  air  space  between  the  battery  and 
the  battery  box  for  ventilation.  The  interior  of  the  battery  box  must 
be  kept  clean  and  dry  and  the  terminals  should  be  coated  with  vase- 
line or  grease.  If  any  acid  is  spilled  on  the  battery  wipe  it  up 
with  waste  wet  with  ammonia.  Never  lay  waste  on  top  of  a  battery 
since  this  practice  is  apt  to  cause  short  circuit  between  the  cells. 

A  battery  should  be  inspected  once  each  week  in  warm  weather 
and  once  every  two  weeks  in  cold  weather  to  ascertain  its  condition. 
If  the  solution  is  low  distilled  water  should  be  added  to  cover  the 
tops  of  the  plates.  Be  very  careful  not  to  add  too  much  water.  At 
each  inspection  several  hydrometer  readings  of  each  cell  must  be 
taken  before  adding  any  water.  After  testing  the  electrolyte  be  sure 
to  replace  it  in  the  cell  to  which  it  belongs.  If  the  specific  gravity 
of  one  cell  shows  it  to  be  considerably  lower  than  the  others  at  several 
successive  readings  this  indicates  the  cell  is  out  of  order.  Likewise, 
if  one  cell  requires  more  water  than  the  other  it  shows  that  the  jar 
is  cracked. 

Never  allow  the  battery  to  get  completely  discharged  because  it 
will  sulphate  the  plates  in  the  battery.  If  the  generator  on  the  car 
does  not  keep  the  battery  up  to  a  reading  of  1.200,  at  least  part  of 
the  time,  the  battery  should  be  removed  and  charged  by  some  outside 
source. 

If  it  is  found  that  the  batteries  read  very  high  at  several  successive 
readings  it  is  best  to  use  some  of  the  current  either  by  running  the 
engine  for  a  few  minutes  with  the  starting  motor  or  by  leaving  the 
lights  turned  on  until  the  battery  is  partially  discharged. 

If  for  any  reason  an  extra  charge  is  needed  and  the  battery  is 
charged  from  some  outside  source  only  direct  current  can  be  used. 
Limit  the  current  to  the  proper  charging  rate  by  connecting  a  suitable 
resistance  in  series  with  the  battery.  Incandescent  lamps  are 
suitable  for  this  purpose.  Connect  the  positive  battery  terminal  to 
the  positive  charging  wire  and  the  negative  to  the  negative  wire. 
If  reversed,  serious  injury  to  the  battery  will  result.  The  proper 
charging  rates  are  generally  marked  on  the  name  plate  of  a  battery. 
When  charging  start  at  the  starting  rate  and  continue  to  charge  at 
this  rate  until  the  cells  gas  freely.  Then  reduce  the  charging  to  the 
finish  rate  and  continue  for  6  hours.  The  specific  gravity  at  the  end 


144  MOTOR  VEHICLES  AND  THEIR  ENGINES 

of  the  charge  should  read  1.280  to  1.300.  If  it  does  not  reach  this 
point  continue  the  charge  at  the  finish  rate  until  the  specific  gravity 
stops  rising.  If  the  specific  gravity  still  does  not  reach  1.280  it 
indicates  that  the  battery  needs  special  attention,  the  trouble  prob- 
ably resulting  from  loss  of  acid  or  sulphating  or  buckling  of  one  or 
more  plates.  If  during  charging  the  tefnperature  of  any  cell  exceeds 
110  degrees  Fahrenheit  the  charging  rate  must  be  reduced. 

During  warm  weather  the  temperature  of  the  battery  must  be 
watched  and  if  the  solution  is  found  to  be  110  degrees  Fahrenheit  the 
lights  should  at  once  be  turned  on  so  as  to  reduce  the  current  passing 
into  the  battery.  Batteries  overheat  when  nearly  fully  charged  if  a 
high  rate  of  charge  is  maintained. 

During  extremely  cold  weather  it  is  essential  that  the  battery  be 
kept  fully  charged  in  order  to  prevent  freezing  of  the  solution  The 
f  ollowing  table  shows  the  temperature  afr  which  electrolyte  of  different 
specific  gravity  will  freeze. 

SP.  GRAVITY  FREEZING  PT. 

1.150  20°  above  0 

1.180  0° 

1.215  20°  below  0 

1.250  60°  below  0 

When  a  battery  is  not  to  be  used  for  a  short  period  of  time,  such 
as  one  or  two  months,  it  should  be  given  a  fresh  charge  once  a  month 
and  a  thorough  charge  before  being  put  back  into  active  service.  In 
case  a  battery  is  to  be  shipped  it  should  be  fully  charged,  the  electro- 
lyte emptied  out,  and  the  plates  thoroughly  washed  in  distilled  water 
and  dried.  It  is  put  in  operation  again  as  previously  described. 

Fig.  108  shows  a  very  good  charging  board  which  is  suitable  for 
charging  a  storage  battery  from  110  volt  direct  current  mains.  The 
charging  is  controlled  by  the  number  of  lamps  in  the  circuit.  The 
lamps  being  connected  in  parallel,  more  current  will  flow  as  the 
number  of  lamps  is  increased. 

Batteries  are  constructed  for  the  particular  service  for  which  they 
are  to  be  used.  A  battery  constructed  for  lighting  purposes  only, 
should  never  be  used  with  starting  systems,  as  the  heavy  discharge 
rate  will  cause  serious  damage  to  the  battery. 


BATTERIES 


145 


Line 


Fuses  not  less 
than  10  Amperes, 


Lamps 


o 
-o- 

o 
o 


-o 


-gj. 

c Double  Pole 

Single  Throw 

Switch 


For  Charging  use 

8.110  Volt -32  C. P.  (100  Watt) 

Carbon  Filament  Lamps 

or 

16-110  Volt-16^.P.  (50  WatO 
Carbon  Filament  Lamps 
or 

20- 110  Volt.  10  Watt 
Tungsten  Lamps 

32-110  Volt-25  Watt 
Tungsten  Lamps 


Fig.  108 — Charging  Board 


CHAPTER  XV 


INDUCTION 

When  electricity  is  produced  by  chemical  means  the  voltage  is 
low  and  therefore  is  not  suitable  for  ignition  systems  unless  the 
voltage  is  increased  in  some  manner.  High  voltages  are  obtained  by 
electro-magnetic  induction  and  this  method  of  obtaining  higher 
voltages  is  applied  to  ignition  systems.  To  thoroughly  understand 
ignition  it  is  necessary  to  study  the  elementary  principles  under- 
lying induction  which  will  be  taken  up  in  this  chapter. 

The  exact  nature  of  magnetism  and  electricity  is  still  unknown 
but  much  has  been  discovered  concerning  the  relation  existing 
between  them.  It  has  been  shown  that  whenever  there  is  a  current 
of  electricity  flowing  there  is  always  a  magnetic  field  present.  This 
magnetic  field  lasts  as  long  as  the  current  continues  to  flow  showing 
that  there  is  a  definite  relation  existing  between  magnetism  and 
electricity.  Since  electricity  produces  magnetism  it  is  reasonable  to 
expect  magnetism  to  produce  electricity  and  it  has  been  found  by 
experiment  that  this  is  true. 


Fig.  109 — Electro-Magnetic  Induction 

If  a  magnetic  field  is  present  and  a  loop  of  wire  is  moved  so  as 
to  cut  the  magnetic  lines  of  force  (Fig.  109)  a  current  is  caused  to 
flow  through  the  conductor.  Currents  generated  in  this  way  are 
known  as  induced  currents  and  the  phenomenon  termed  electro- 
magnetic induction.  The  same  result  is  obtained  if  the  conductor 
is  kept  stationary  and  the  magnetic  lines  of  force  moved  so  as  to 
be  cut  by  the  conductor. 

146 


INDUCTION 


147 


Fig.  110— Right-Hand 
Rule 


The  direction  of  the  flow  of  the  induced  current  in  the  conductor 
will  depend  upon  the  direction  of  the  lines  of  force  and  the  direction 
in  which  the  magnetic  field  is  cut.  A  simple  method  of  determining 
this  when  the  direction  of  motion  and  direction  of  the  lines  of  force 
are  known  is  by  means  of  the  right  hand  rule.  Place  the  thumb,  the 
first,  and  the  second  fingers  of  the  right 
hand  all  at  right  angles  to  each  other  (Fig. 
110)  and  in  such  relation  to  the  conductor 
that  the  first  finger  points  in  the  direction 
of  the  lines  of  force,  and  the  thumb  in  the 
direction  of  motion.  The  second  finger  will 
then  indicate  the  direction  of  the  induced 
current.  Applying  this  rule  to  Fig.  110  in 
which  the  wire  is  being  moved  upward  and 
the  lines  of  force  flow  from  the  north  pole 
as  indicated,  the  current  is  found  to  flow  through  the  conductor  as 
indicated  by  the  arrow. 

The  strength  of  the  induced  voltage  in  a  conductor  when  it  is 
cutting  lines  of  force  is  proportional  to  the  rate  at  which  the  lines  of 
force  are  cut.  If  a  circuit  of  several  turns  of  wire  is  substituted  for 
the  single  loop  used  in  Fig.  109  the  induced  voltage  will  be  greater. 
This  results  because  each  loop  now  cuts  as  many  lines  of  force  as 
were  cut  by  a  single  loop  increasing  the  total  number  of  lines  of  force 
cut.  If  the  strength  of  the  magnet  is  increased  it  will  cause  more 
lines  of  force  to  be  set  up  so  that  the  same  number  of  turns  moving 
through  the  field  would  cut  a  greater  number  of  lines  of  force  thus 
causing  an  induced  current  of  higher  voltage.  The  induced  voltage 
will,  therefore,  depend  upon  the  following  factors: 

1.  The  strength  of  the  magnetic  field. 

2.  The  speed  or  rate  of  cutting  lines  of  force, 

3.  The  number  of  turns  of  wire  cutting  the  lines  of  force. 


Fig.  Ill— Self  Induction 


148 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


SELF  INDUCTION. — If  a  coil  of  wire  is  placed  about  a  core  of 
soft  iron,  and  current  sent  through  the  coil,  magnetic  lines  of  force 
will  be  set  up.  If  the  circuit  is  broken  by  opening  the  switch  "A" 
(Fig.  Ill)  the  current  ceases  to  flow  and  the  magnetic  field  will 
collapse.  In  collapsing  the  lines  of  force  cut  the  winding  of  the  coil 
inducing  current  in  the  coil  which  is  called  self  induction.  Self 
induction  is  defined  as  "the  cutting  of  a  wire  or  coil  by  the  lines  of 
force  set  up  by  the  current  flowing  through  it."  Applying  the  right 
hand  rule  it  will  be  seen  that  the  direction  of  flow  of  the  induced 
current  is  in  the  same  direction  as  the  interrupted  flow  of  current. 
When  applying  the  right  hand  rule  do  not  take  the  motion  of  the 
lines  of  force  as  the  direction  of  motion  but  take  the  equivalent 
motion  of  the  conductor. 

The  induced  voltage  will  be  much  higher  than  that  of  the  current 
which  set  up  the  magnetic  field.  When  the  switch  is  opened  this 
high  induced  voltage  causes  an  arcing  between  the  separating  con- 
tacts. When  self  induction  is  present  in  an  ignition  system  the 
induced  voltage  is  approximately  200  volts,  which  is  not  sufficiently 
high  to  jump  a  fixed  air  gap  of  any  appreciable  size  but  will  cause  a 
following  arc  between  separating  points. 

When  the  circuit  is  made  the  magnetic  field  building  up  also  cuts 
the  winding.  By  applying  the  right  hand  rule  it  will  be  seen  that  the 
induced  current  opposes  the  flow  of  the  current  setting  up  the  field. 
This  is  termed  counter  electro-motive-force  and  its  opposition  to  the 
increasing  current  in  the  coil  causes  the  field  to  build  up  very  slowly. 


Fig.  112 — Mutual  Induction 

MUTUAL  INDUCTION.— If  two  coils  of  wire  are  placed  about  an 
iron  core  and  current  caused  to  flow  through  one  of  them  (Fig.  112) 
a  magnetic  field  will  be  built  up  about  the  core.  The  coil  through 


INDUCTION  149 

which  this  current  is  caused  to  flow  is  known  as  the  primary  and  the 
other  coil  is  called  the  secondary.  If  the  switch  "  A  "  is  now  suddenly 
opened  this  magnetic  field  collapses  and  both  windings  are  cut  by 
the  lines  of  force.  This  causes  currents  to  be  induced  in  both  the 
primary  and  secondary  windings,  that  in  the  secondary  is  said  to  be 
mutually  induced  current.  Mutual  induction  is  defined  as  "the 
cutting  of  a  wire  or  coil  by  lines  of  force  set  up  by  current  flowing 
through  another  wire  or  coil."  There  is  no  electrical  connection 
between  the  primary  and  secondary  windings.  By  applying  the 
right  hand  rule  it  will  be  seen  that  the  induced  current  in  the  second- 
ary flows  in  the  opposite  direction  to  the  inducing  current  in  the 
primary  when  the  primary  circuit  is  made  and  in  the  same  direction 
when  the  primary  circuit  is  broken. 

When  the  primary  circuit  is  made  a  counter  E.  M.  F.  results 
which  tends  to  oppose  the  building  up  of  the  field.  The  mutually 
induced  current  in  the  secondary  sets  up  a  field  which  tends  to 
strengthen  this  counter  E.  M.  F.,  further  retarding  the  building  up 
of  the  magnetic  field.  Thus  the  current  flowing  in  the  primary 
has  to  overcome  the  counter  E.  M.  F.  due  to  the  induced  current. 
Hence  the  rate  at  which  the  field  builds  up  is  slow  and  the  resulting 
voltage  in  the  secondary  will  be  correspondingly  low.  When  the 
primary  circuit  is  broken,  however,  there  is  no  counter  E.  M.  F. 
in  the  primary;  the  result  is  a  sudden  collapse  of  the  field  and  a 
consequently  high  voltage  is  induced  in  the  secondary. 

When  high  voltages  are  desired,  they  may  be  obtained  by  mutual 
induction,  employing  a  much  greater  number  of  turns  of  wire  in  the 
secondary  winding  than  in  the  primary.  The  voltages  in  the  primary 
and  secondary  windings  vary  directly  as  the  number  of  turns  of  wire 
in  each  while  the  current  varies  inversely  as  the  number  of  turns  of 
wire.  For  this  reason  fine  wire  is  used  for  the  secondary  winding  and 
much  heavier  wire  for  the  primary. 

Fig.  113  shows  a  simple  vibrator  which  is  used  for  making  and 
breaking  the  circuit.  It  consists  of  a  coil  wound  about  a  soft  iron 
core  "A";  opposite  one  end  of  this  core  is  placed  a  small  piece  of 
soft  iron  "B"  attached  to  a  spring  "C."  An  adjusting  screw  "D" 
is  in  contact  with  the  spring  when  in  its  normal  position. 

One  side  of  the  battery  is  grounded  while  the  other  is  connected 
through  the  switch  "  S ' '  to  the  coil,  the  other  end  of  the  coil  is  attached 
to  the  spring.  "C"  and  the  screw  "D"  is  grounded. 

When  the  switch  is  closed  a  magnetic  field  is  set  up  magnetizing 
the  core.  This  attracts  the  iron  "B"  breaking  the  circuit  at  "D." 
This  causes  the  core  to  be  demagnetized  and  the  spring  "C"  returns 
to  its  normal  position,  again  closing  the  circuit.  This  operation  will 


150 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


Fig.  113 — Simple  Vibrator 


be  repeated  over  and  over  as  long  as  the  switch  "S  "  is  closed.     Thus 
the  circuit  is  automatically  made  and  broken. 

When  the  circuit  is  broken 
the  collapse  of  the  magnetic 
field  induces  a  current  in  the 
winding.  The  voltage  of  this 
self-induced  current  is  sufficient 
to  cause  an  arc  to  follow  the 
separating  points  at  "D"  each 
time  the  current  is  broken. 
This  arcing  burns  and  pits  the 
contact  points  increasing  the 
resistance  of  the  circuit.  To 
prevent  this  a  condenser  "K" 
is  connected  in  parallel  with  the 
contact  points  as  shown  in 
Fig.  113.  When  the  circuit  is 
broken  the  flow  of  induced 
current  passes  into  the  conden- 
ser charging  it.  This  momen- 
tarily diverts  the  flow  of  current  from  the  contact  points  allowing 
them  to  separate  sufficiently  to  prevent  a  following  arc. 

A  condenser  is  usually  constructed  of  sheets  of  silver,  tin,  or  lead 

foil,  alternate  sheets  being 
connected  to  common  ter- 
minals and  separated  from  each 
other  by  some  insulating  ma- 
terial such  as  mica  or  specially 
treated  paper  (Fig.  114). 

The  capacity  of  a  conden- 
ser depends  upon  the  total 
area  of  the  plates  and  the 
distances  these  plates  are  sepa- 
rated by  the  insulating  mater- 
ial. When  a  condenser  is  used 
on  ignition  systems  it  is  neces- 
sary to  have  it  of  proper  capa- 
city. This  is  governed  by  the 
amount  of  self -induced  current  in  the  circuit  in  which  it  is  placed. 


Fig.  114 — Condenser 


CHAPTER  XVI 


BATTERY  IGNITION  SYSTEMS 

After  experimenting  for  many  years  with  different  systems  of 
ignition  it  has  been  found  that  the  most  reliable  and  satisfactory 
is  the  high  tension  "jump  spark"  system.  There  are  many  means 
employed  to  produce  the  necessarily  high  voltage  required  to  jump 
a  set  gap,  all  of  which  are  based  on  the  principle  of  mutual  electro- 
magnetic induction.  Ignition  systems  are  classified  under  two 
general  headings,  Battery  Ignition  Systems  and  Magneto  Ignition 
Systems.  Battery  ignition  systems  employ  a  coil  to  obtain  the  neces- 
sary voltage  receiving  the  current  for  the  primary  from  some  outside 
source.  This  type  of  ignition  system  will  be  discussed  in  this  chapter. 


Fig.  115 — Induction  Coil 

Fig.  115  shows  a  core  "A"  wound  with  a  primary  and  secondary 
winding,  one  end  of  the  primary  being  connected  to  the  battery,  the 
other  side  of  which  is  grounded.  The  other  end  of  the  primary  is 
connected  to  ground  through  a  switch  "  S . "  One  end  of  the  secondary 
is  grounded  and  the  other  end  led  to  a  spark  gap  "G,"  the  other  side 
of  which  is  grounded. 

When  the  switch  is  closed  a  magnetic  field  is  set  up  about  the  core 
which  collapses  when  the  switch  is  opened,  causing  a  mutually  induced 
current  to  flow  in  the  secondary.  In  ignition  coils  a  great  number 
of  turns  of  wire  are  used  on  the  secondary  to  obtain  sufficient  voltage 
to  jump  set  air  gaps. 

As  already  explained  in  timing  the  spark  must  occur  at  a  certain 
definite  time  during  the  operation  of  the  engine.  This  requires  that 
the  primary  circuit  be  made  and  broken  to  obtain  the  mutually 


151 


152  MOTOR  VEHICLES  AND  THEIR  ENGINES 

induced  current  in  the  secondary  at  the  proper  time.  To  accomplish 
this  some  circuit  breaking  device  positively  driven  by  the  engine  and 
timed  with  it  must  be  used.  Such  a  device  is  known  as  "Timer" 
and  its  object  is  to  make  and  break  the  primary  circuit  at  the  proper 
time. 


Fig.  116— Closed  Circuit  Timer       Fig.  Ill— Open  Circuit  Timer 

There  are  two  types  of  timers,  that  shown  in  Fig.  116  where  the 
contacts  are  together  except  when  separated  by  the  cam,  and  that 
shown  in  Fig.  117  where  the  contacts  are  separated  except  when 
closed  by  the  cam.  The  first  type  allows  the  current  to  flow  through 
the  primary  except  for  the  short  period  when  the  circuit  is  broken. 
The  circuit  being  closed  the  greater  part  of  the  time  the  current  con- 
sumption will  consequently  be  large.  The  other  type  allows  current 
to  flow  through  the  primary  only  for  an  instant  which  materially 
reduces  the  current  consumption.  When  the  circuit  is  made  in  this 
construction  the  flow  of  the  current  through  the  primary  is  opposed 
by  the  counter  E.  M.  F.  resulting  from  self-induction  and  the  com- 
plete building  up  of  the  magnetic  field  takes  a  definite  length  of  time. 
At  slow  speed  there  will  be  enough  time  elapsed  before  the  circuit  is 
again  broken  for  the  complete  building  up  of  the  field.  As  the  speed 
increases  there  is  not  sufficient  time  and  the  field  will  still  continue 
to  build  up  due  to  the  inertia  of  the  current  after  the  circuit  has  been 
broken.  Therefore,  the  collapse  of  the  field  and  consequent  mutual 
induction  in  the  secondary  does  not  occur  for  some  time  after  the 
primary  circuit  has  been  broken.  This  is  known  as  "electrical  lag" 
and  is  measured  in  degrees  of  revolution  of  the  crank  shaft  between 
point  of  break  and  point  of  spark.  On  some  ignition  systems  this 
lag  has  been  measured  and  found  to  be  as  great  as  35°  at  2,000 
R.  P.  M.  of  the  engine. 

If  the  cams  (Figs.  116  and  117)  are  turned  clockwise  and  the 
housing  carrying  the  contact  points  is  turned  anti-clockwise  the 


BATTERY  IGNITION  SYSTEMS 


153 


circuit  will  be  broken  earlier.  This  will  advance  the  time  at  which 
the  spark  takes  place  in  the  cylinder  and  is  termed  "advancing  the 
spark."  If  the  housing  were  moved  in  a  clockwise  direction  it  would 
cause  the  circuit  to  be  interrupted  later  and  consequently  the  spark 
would  take  place  later  in  the  cylinder.  This  is  termed  "retarding 
the  spark."  The  general  rule  is  that  when  the  housing  is  turned  in 
the  opposite  direction  to  the  rotation  of  the  cam  the  spark  is  advanced 
and  when  turned  in  the  same  direction  the  spark  is  retarded. 

It  will  be  remembered  from  valve  timing  that  ignition  is  advanced 
in  accordance  with  the  speed  of  the  engine.  Hence,  it  is  necessary 
to  limit  the  movement  of  the  timer  housing.  The  method  of  ac- 
complishing this  varies  with  the  type  of  timing  connection  employed. 

The  cam  used  in  a  timer  may  have  any  number  of  noses  but  it 
generally  has  as  many  as  the  engine  has  cylinders.  This  makes  it 
necessary  to  drive  the  timer  at  half  engine  speed  on  a  four-cycle 
engine.  To  determine  the  speed  at  which  any  timer  should  be  driven- 
the  following  formulae  are  used: 

For  four-cycle  engine, 

Number  of  Cylinders 
Speed  =  - 

2  x  number  of  noses  on  cam. 

For  two-cycle  engines, 

„  *    ,  _  Number  of  Cylinders 

Number  of  noses  on  cam. 

Applying  the  formula  for  four-cycle  to  a  four-cylinder  engine 
having  a  four-nosed  timing  cam : 

Speed  =  -      -  =  —  engine  speed. 


Fig.  118 — Induction  Coil  with  Timer  and  Condenser 

In  Fig.  118  the  switch  has  been  replaced  by  a  timer  and  a  con- 
denser has  been  connected  in  parallel  with  it.     The  condenser  is 


154  MOTOR  VEHICLES  AND  THEIR  ENGINES 

necessary  just  as  in  the  case  of  a  vibrator  the  self-induction  otherwise 
causing  arcing  at  the  contact  points. 

If  continued  arcing  at  the  contact  points  were  permitted  burning 
and  pitting  would  result  which  would  increase  the  resistance  of  the 
primary  circuit.  Any  increased  resistance  in  the  primary  circuit 
reduces  the  amount  of  current  flowing,  thus  weakening  the  magnetic 
field.  This  reduction  of  the  lines  of  magnetic  force  will  correspond- 
ingly reduce  the  induced  voltage  of  the  secondary  and  material  re- 
duction of  the  secondary  voltage  will  affect  the  spark  or  stop  it 
altogether.  Low  secondary  voltage  is  generally  traceable  to  the 
primary  circuit. 

For  the  timer  to  operate  properly  it  is  necessary  that  the  contact 
points  be  in  proper  adjustment.  The  gap  should  be  0.5  mm.  or 
0.020  inch  when  the  points  are  fully  separated.  If  the  gap  is  too 
small  arcing  will  take  place  causing  pitting  of  the  contact  points. 

The  timer  controls  the  instant  at  which  the  spark  occurs  and  must 
operate  in  synchronism  with  the  engine.  However,  if  the  system  is 
to  be  used  on  a  multi-cylinder  engine  some  provision  must  be  made 
to  distribute  the  secondary  current  to  the  spark  plugs  in  their  proper 
firing  order.  To  accomplish  this  a  distributor  is  used. 


Fig.  119 — Flush  Segment  Distributor 

Fig.  119  shows  one  common  construction  of  distributor.  The 
current  is  led  to  the  center  terminal  which  is  in  contact  with  the 
rotor.  This  rotor  is  made  of  insulating  material  and  has  a  brass  tube 
running  through  it  in  which  fits  the  carbon  brush  which  conducts  the 
current  to  the  segments.  The  housing  is  made  of  insulating  material 
with  brass  segments  inserted  in  it  and  flush  with  the  inner  circum- 
ference with  which  the  carbon  brush  of  the  rotor  makes  contact. 
The  segments  are  connected  by  brass  tubes  through  the  insulating 
material  to  the  terminals  on  the  outer  surface  of  the  distributor.  As 
the  rotor  revolves  it  makes  contact  with  the  segments  in  order  and 
the  terminals  connected  to  these  segments  are  wired  to  the  spark 
plugs  in  their  proper  firing  order.  It  is  necessary  to  have  this  rotor 
positively  driven  by  the  engine  and  at  such  a  speed  that  it  will  be 


BATTERY  IGNITION  SYSTEMS  155 

on  the  proper  segment  when  the  primary  circuit  is  broken  by  the 
timer. 

As  it  is  necessary  to  have  a  segment  for  each  cylinder  the  speed  is 
figured  by  using  the  same  formulae  as  employed  in  determining  the 
speed  of  a  timer.  It  will  be  found  that  the  rotor  always  turns  half 
engine  speed  on  a  four-cycle  engine  and  engine  speed  on  a  two-cycle 
engine. 

As  previously  stated  timers  are  usually  designed  with  cams  having 
the  same  number  of  noses  as  there  are  cylinders.  This  permits  the 
timer  and  distributor  to  be  driven  at  the  same  speed  so  that  they  can 
be  incorporated  in  one  unit  and  driven  by  the  same  shaft.  This 
arrangement  is  called  a  timer-distributor  and  the  rotor  of  the  dis- 
tributor is  superimposed  on  the  timer  cam  so  that  it  fits  only  in  one 
position  and  the  distributor  housing  is  keyed  to  the  timer  housing. 
This  construction  assures  the  proper  relation  of  timer  and  distributor 
but  it  must  be  borne  in  mind  that  there  is  no  electrical  connection 
between  them. 

When  a  carbon  brush  distributor  is  used  the  brush  is  always 
in  contact  with  the  inner  surface  of  the  distributor,  part  of  which  is 
insulating  material  between  the  segments.  This  continual  rubbing 
of  the  carbon  brush  over  the  surface  often  causes  a  carbon  deposit  to 
be  formed  which  short-circuits  the  segments  allowing  the  current 
to  flow  to  the  spark  plug  in  the  cylinder  which  offers  the  least  re- 
sistance. This  will  cause  misfiring  of  the  engine. 


Fig.  120 — Raised  Segment  Distributor 

Fig.  120  shows  a  distributor  having*  metal  segments  raised  above 
the  insulation  and  employing  a  metal  brush.  This  design  eliminates 
short  circuiting  of  the  segments. 

Fig.  121  shows  a  distributor  placed  in  the  secondary  circuit  and 
connected  to  the  spark  plugs.  This  completes  the  wiring  of  a 
typical  battery  ignition  system  for  a  four-cylinder  engine. 


156 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


Fig.  121  —  Wiring  of  Battery  Ignition  System 

SPARK  PLUGS.  —  On  high  tension  ignition  systems  it  is  necessary 
to  have  some  device  in  each  cylinder  to  maintain  &  gap  of  definite 
size  across  which  the  secondary  current  must  jump  to  complete  its 
circuit.  This  device  is  known  as  a  spark  plug. 

Fig.  122  shows  a  typical  spark  plug  in  cross 
section.  The  central  electrode  should  be  made 
of  some  material  which  will  not  pit  easily  from 
the  heat  of  the  spark,  such  as  chrome  nickel- 
steel.  This  is  insulated  from  ground  by  insu- 
lating material  which  may  be  composed  of 
porcelain,  mica,  or  steatite.  The  insulator 
must  perform  three  functions:  First,  it  must 
have  sufficient  dielectric  efficiency  to  insulate 
the  central  electrode  from  the  ground;  second, 
it  must  present  a  surface  in  the  combustion 
chamber  to  which  carbon  will  not  readily 
adhere;  third,  it  must  not  crack  under  the 
intense  heat  in  the  cylinder.  Insulators  are 
finished  with  a  highly  polished  surface  which 
should  not  under  any  circumstances  be  scraped 
as  tn*s  wou^  permit  carbon  to  adhere  to  the 
Section  of  Spark  surface.  Some  plugs  are  made  so  that  the 
Plug  insulators  can  be  removed  for  replacement,  in- 

spection, or  cleaning  (Fig.  123). 

This  necessitates  a  gas-tight  joint  between  the  insulator  and  shell 
which  is  usually  obtained  by  screwing  a  bushing  down  against  a 
gasket.  When  porcelain  insulators  are  used  there  must  be  enough 
"give"  at  this  joint  to  allow  for  expansion  of  the  insulator  or  it  will 


Fig.    122—  Cross- 


BATTERY  IGNITION  SYSTEMS 


157 


RUBY  INDIA 
MICA  INSULATION 
LATERALLY  WOUND 


COPPER .J 

ASBESTOS  GASKET  \ 
POSITIVE  GAS  TIGHT  f 
JOINT 


SMALL 

COMPRESSION 
SPACE 


Green  Jacket 


UNSCREW  HERE 
-*- FOR  CLEANING 


EXTRA  HEAVY 
SPARKING  POINTS 


Fig.  123— Plug  with  Removable 
Insulator 


be  cracked.  The  body  of  the  plug  is  usually  made  of  steel,  the  lower 
part  of  which  is  threaded  to  fit  the  thread  in  the  cylinder.  These 
threads  are  made  up  in  three 
sizes:  the  half-inch,  with  ta- 
pered pipe  thread;  the  %  inch 
S.  A.  E.  standard,  with  straight 
thread;  the  18  mm.  metric, 
with  straight  thread.  On  the 
%  inch  and  metric  plugs  a 
shoulder  is  provided  the  pur- 
pose of  which  is  to  tighten 
down  on  a  gasket  when  the 
plug  is  screwed  into  the  cy- 
linder. This  is  not  necessary 
with  a  half-inch  plug  because 
of  the  tapered  thread  which 
becomes  gas  tight  as  it  is 
screwed  into  the  cylinder.  At- 
tached to  the  body  of  the  plug 
is  a  small  electrode  which 
governs  the  size  of  the  spark 
gap.  By  bending  this  elec- 
trode toward  or  away  from  t^ie  central  electrode  the  size  of  the 
gap  is  regulated  to  give  the  best  results.  For  battery  ignition 
this  gap  should  be  between  l/w  and  1/32  of  an  inch  and  for  magneto 
ignition  between  1/64  and  l/5Q  of  an  inch. 

The  results  obtained  from  an  engine  are  largely  dependent  upon 
the  location  of  the  spark  plugs.  When  two  independent  ignition 
systems  are  used,  that  is,  battery  ignition  for  starting  and  magneto 
ignition  for  running,  using  two  separate  spark  plugs,  the  one  that  is 
nearest  the  inlet  valve  should  be  connected  to  the  magneto  ignition 
system.  The  usual  installation  of  plugs  for  this  type  of  ignition  is 
to  place  one  directly  over  the  inlet  valve  and  the  other  over  the  ex- 
haust valve.  As  the  best  mixtures  will  be  nearest  the  inlet  valve  the 
system  which  should  be  used  for  continuous  running  should  be 
wired  to  these  plugs,  while  the  other  should  be  wired  to  the  system 
used  for  starting. 

Fig.  124A  shows  a  spark  plug  properly  installed  in  a  recessed 
spark  plug  cap.  It  can  be  seen  that  the  electrodes  project  slightly 
into  the  combustion  chamber  and  the  best  results  are  obtained 
under  these  conditions. 

Fig.  124B  shows  a  standard  plug  installed  in  an  unrecessed  spark 
plug  cap.  It  is  seen  that  the  electrodes  of  the  plug  do  not  extend 


158 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


Fig.  124 — Spark  Plug  Locations 

into  the  combustion  chamber  and  a  pocket  is  formed.  After  a  charge 
has  been  fired  and  the  piston  comes  up  on  the  exhaust  stroke  it  will 
compress  burned  gases  in  this  pocket.  Therefore,  on  the  following 
compression  stroke  some  of  the  fresh  mixture  will  be  compressed  in 
this  pocket  where  it  will  mix  with  the  pocketed  exhaust  gas  causing 
a  very  poor  mixture.  The  mixture  is  so  poor  in  some  cases  that  it 
will  not  ignite  and  causes  misfiring  of  the  engine.  If  the  charge  does 
ignite  the  rate  of  flame  propagation  will  be  reduced  causing  a  loss  of 
power. 


Fig.  125— Vibrating  Induction  Coil 


BATTERY  IGNITION  SYSTEMS  159 

Fig.  124C  shows  a  spark  plug  passing  directly  through  the  water- 
jacket  without  a  recessed  spark  plug  cap  being  used.  Although  the 
electrodes  project  into  the  combustion  space  this  installation  is  not 
entirely  satisfactory  because  it  is  necessary  to  have  a  special  design 
of  plug  for  each  engine.  Many  times  it  is  impossible  to  obtain  exact 
length  of  plug  necessary  to  bring  the  electrodes  flush  with  the  cylinder 
walls.  This  makes  it  imperative  to  use  either  spark  plug  caps  that 
will  take  standardized  plugs  or  else  use  a  special  plug  designed  for 
that  particular  engine. 

If  a  second  winding  of  a  great  many  turns  of  fine  wire  is  wound  on  a 
simple  vibrator  coil  such  as  shown  in  Fig.  113  a  spark  coil  is  obtained. 
Fig.  125  shows  such  a  coil,  one  end  of  the  secondary  being  grounded 
while  the  other  is  led  to  a  spark  gap  "G,"  the  other  side  of  which  is 
grounded.  When  the  switch  "S"  is  closed  the  vibrator  "  V"  rapidly 
makes  and  breaks  the  primary  circuit  as  already  explained.  This 
causes  a  magnetic  field  to  be  alternately  built  up  and  broken  down 
inducing  a  current  of  high  voltage  in  the  secondary  which  can  jump 
the  spark  gap  to  the  ground. 

If  this  spark  gap  is  inside  the  cylinder  of  an  engine  the  explosive 
mixture  will  be  fired  when  the  switch  "S"  is  closed  which  will  cause 
a  spark  to  jump  the  gap.  In  this  way  the  spark  coil  is  used  for  igni- 
tion purposes.  It  was  applied  to  early  ignition  systems  and  still 
may  be  found  on  a  few  machines. 

Fig.  126  shows  a  four-unit  coil  system  in  which  four  separate  spark 
coils  are  used.  One  side  of  the  battery  "B"  (or  other  source  of 
current)  is  grounded  while  the  other  is  connected  to  the  primary 
windings  of  the  coils  "C,"  "D,"  "E,"  and  "F."  The  other  ends  of 
the  primaries  are  connected  through  the  vibrators  "V"  to  the  con- 
tact segments  of  a  revolving  switch  "S"  sometimes  called  a  "com- 
mutator." Across  each  of  the  vibrators  is  connected  a  condenser  "K." 
The  rotor  "R"  of  the  switch  "S"  is  positively  driven  by  the  engine 
and  is  connected  to  ground,  successively  completing  the  circuits 
through  the  contact  segments.  Since  there  are  as  many  segments 
as  there  are  cylinders  it  must  be  driven  at  half  engine  speed.  One 
end  of  each  secondary  is  connected  to  its  primary  through  which  it 
is  grounded,  while  the  other  end  is  wired  to  a  particular  spark  plug, 
depending  upon  the  firing  order  of  the  engine.  When  the  revolving 
rotor  touches  one  of  the  contacts,  current  from  the  battery  flows 
through  the  coil  connected  to  it,  causing  its  vibrator  rapidly  to  make 
and  break  the  primary  circuit.  This  induces  high  voltage  impulses 
of  current  in  the  secondary  and  sparks  jump  the  gap  at  the  spark 
plug  to  which  the  secondary  is  connected.  This  is  identical  with  the 


160 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


Fig.  126— Four-Unit  Coil  Ignition  System 


Fig.  1271— Four-Unit  Coil  System  with  Master  Vibrator 


BATTERY  IGNITION  SYSTEMS 


161 


Ford  system  in  which  the  current  is  supplied  by  a  low  tension 
magneto  instead  of  a  battery. 

This  system  eliminates  the  necessity  for  a  distributor  but  makes 
four  separate  spark  coils  necessary,  each  with  a  vibrator  to  be  kept 
in  adjustment  and  contacts  to  clean.  It  is  practically  impossible  to 
adjust  all  the  vibrators  so  that  the  spring  tension  is  the  same  on  each. 
This  causes  the  sparks  in  the  different  cylinders  to  vary  in  intensity 
and  uneven  running  of  the  engine  results. 

To  remedy  this  difficulty  a  Master  Vibrator  may  be  installed  in 
the  system.  This  consists  of  a  vibrating  coil  having  but  one  winding 
which  is  connected  in  the  primary  circuit  as  shown  in  Fig.  127.  All 
the  spark  coils  are  non-vibrating  or  if  vibrating  coils  are  installed  the 
contact  screws  should  be  screwed  down  so  they  hold  the  springs 
tight  against  the  iron  cores  of  the  coils. 

When  the  rotary  switch  "S"  touches  one  of  the  contacts,  current 
flows  from  the  battery  "A"  through  the  master  vibrator  "M" 
and  coil  "A,"  "B,"  "C,"  or  "D,"  depending  upon  which  contact  is 
touched.  The  vibrator  "V"  makes  and  breaks  the  primary  circuit, 
inducing  current  in  the  secondary  winding  of  the  spark  coil  just  as 
when  it  had  its  own  vibrator.  This  makes  it  possible  to  get  the  same 
intensity  of  spark  in  all  the  cylinders  with  but  one  vibrator  to  adjust. 

NORTHEAST  IGNITION  SYSTEM 

The  complete  ignition  system  consists  essentially  of  three  self- 
contained  units;  the  single  unit  coil,  the  timer  and  distributor 


Fig.  128— Unit  Assembly 


162  MOTOR  VEHICLES  AND  THEIR  ENGINES 

assembly,  and  the  automatic  advance.  Each  of  these  three  units  is 
constructed  so  as  to  be  easily  removed  for  repairs  and  replacement 
(Fig.  128). 

The  coil  is  constructed  to  operate  on  12  volts.  It  differs  from  the 
ordinary  coil  in  having  both  ends  of  the  primary  brought  out  to 
terminals  on  the  coil  housing.  As  usual,  one  end  of  the  secondary  is 
grounded  while  the  other  is  connected  to  a  stud  on  the  side  of  the 
coil  and  this  stud  is  connected  to  an  insulated  binding  post  on  the 
side  of  the  coil  housing.  Around  this  post  is  a  raised  section  of  the 
housing  designed  to  act  as  a  safety  spark  gap.  If  at  any  time  the 
resistance  between  this  post  and  the  ground  at  the  spark  plug  be- 
comes greater  than  that  of  this  air  gap  the  current  will  jump  from 
the  post  to  the  housing,  relieving  the  pressure  in  coil  so  that  the  insula- 
tion will  not  be  broken  down.  When  sparking  occurs  at  this  point 
it  is  usually  an  indication  of  a  broken  or  disconnected  cable  or  too 
wide  a  gap  at  the  spark  plug. 


Fig.  129— Timer  with  Condenser 

The  timer  (Fig.  129)  is  typical  of  the  construction  used  for 
saturated  coils.  Both  contacts  of  this  timer  are  insulated  from  the 
ground  and  the  condenser  is  wired  in  parallel  with  the  contact  points 
and  contained  in  the  timer  housing.  This  makes  the  condenser 
accessible  and  easy  to  replace,  but  it  must  be  remembered  that  the 
condenser  must  be  of  a  certain  capacity  which  is  determined  by  the 
coil.  Therefore,  when  replacing  a  condenser  one  designed  for  this 
coil  must  be  used. 


BATTERY  IGNITION  SYSTEMS 


163 


Fig.  130 — Automatic  Spark 
Advance 


The  distributor  is  of  the  flush  segment  type  using  a  metal  brush. 
The  rotor  is  superimposed  upon  the  timer  cam  both  being  driven  by 
the  same  vertical  shaft. 

There  are  two  methods  for  advancing  and  retarding  the  spark  on 
this  system.  The  manual  control  moves  the  housing  carrying  the 
contact  points,  this  movement  being  limited  so  that  further  advance 
must  be  accomplished  by  the  automatic  device.  The  automatic 
control  (Fig.  130)  is  operated  by  cen- 
trifugal action  so  that  as  the  speed 
increases,  the  shaft  operating  the 
timer  cam  is  advanced  with  respect 
to  the  operation  of  the  engine,  the 
reverse  taking  place  as  the  speed  is 
diminished.  Since  the  timing  of  the 
ignition  is  partially  dependent  upon 
the  speed  of  the  engine  this  dual  control  proves  very  satisfactory. 

Fig.  131  is  a  wiring  diagram  showing  the  internal  wiring  of  this 
system  as  applied  to  the  Dodge  Car  and  Fig.  132  shows  the  actual 
external  connections.  One  end  of  the  primary  is  connected  to  the 
ignition  switch  while  the  other  end  is  connected  to  one  of  the  timer 
terminals.  The  switch  is  arranged  so  there  are  two  "on"  and  two 
"off"  positions.  In  one  "on"  position  the  current  passes  through 
the  primary  of  the  coil,  then  through  the  timer  and  back  to  the 
switch  where  it  is  grounded.  In  the  other  "on"  position  the  cur- 
rent passes  through  the  timer  and  then  through  the  primary  winding 
in  the  opposite  direction  returning  to  the  switch  where  it  is  grounded. 
The  object  of  a  switch  of  this  kind  is  to  cause  the  current  to  pass 
through  the  primary  in  the  opposite  direction  each  time  the  switch 

position.     If  the  current  flows  through  a 


STABTING  SWITCH 


Fig.  131 — Internal  Wiring  Diagram 


164 


BATTERY  IGNITION  SYSTEMS 


165 


primary  each  time  in  the  same  direction  the  soft  iron  core  will  retain 
some  of  its  magnetism  after  the  circuit  is  broken.  This  prevents  a 
complete  breaking  down  of  the  magnetic  field  and  will  lower  the  self 
and  mutually  induced  voltage.  This  is  prevented  by  building  up 
the  field  each  time  in  the  opposite  direction. 

DELCO  IGNITION  SYSTEM 

This  ignition  system  is  made  up  of  two  self-contained  units,  the 
coil    assembly    and   timer-distribution    assembly    with    automatic 


To 


W//f£3 


Fig.  133 — Unit  Assembly 


advance.    The  coil  housing  can  easily  be  attached  to  the  timer 
distributor  housing  as  shown  in  Fig.  133. 

The  coil  is  wound  for  6  volts  but  has  a  resistance  connected  in 
series  with  the  primary  so  that  it  may  be  used  on  a  12-volt  circuit. 
There  are  four  terminals  on  the  coil  housing.  The  ends  of  the  primary 
are  connected  to  two  of  these,  one  side  of  the  condenser  is  connected 
to  a  third,  and  the  ungrounded  end  of  the  secondary  is  connected 


166 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


to  the  fourth.  The  condenser  is  contained  in  the  coil  housing  and 
connected  in  parallel  with  the  contact  points. 

The  timer  is  of  the  construction  used  with  a  saturated  coil  both 
contacts  being  insulated  from  the  ground.  The  distributor  is  super- 
imposed upon  the  timer  and  is  of  the  flush  segment  type,  the  rotor 
being  driven  by  the  same  shaft  as  the  timer  cam. 

This  system  has  both  manual  and  automatic  spark  advance.  The 
manual  advance  is  accomplished  in  the  usual  manner  by  moving 
the  housing  carrying  the  contact  points.  The  automatic  advance  is 
of  the  usual  centrifugal  construction  advancing  the  cam  with  relation 
to  the  operation  of  the  engine,  the  amount  of  the  advance  being 
controlled  by  the  speed  of  the  engine. 


Fig.  8 


Fig.  134 — Internal  Wiring  Diagram 

Fig.  134  is  a  wiring  diagram  showing  the  internal  wiring  of  this 
system  as  applied  to  the  Dodge  Car  and  Fig.  135  shows  the  actual 
external  connections.  One  side  of  the  battery  is  grounded  and  the 
other  side  is  connected  to  the  ignition  switch  passing  to  the  starting 
switch  and  through  the  ammeter.  From  this  point  the  current  will 
flow  through  the  ignition  system  in  two  ways  and  is  governed  by  the 
position  of  the  switch  when  in  the  "on"  position.  The  switch  is  so 
arranged  that  it  causes  the  current  to  flow  first  in  one  direction  and, 
in  the  other  "on"  position,  in  the  opposite  direction.  One  path  is 
as  follows:  The  current  flows  to  the  coil  passing  through  the  re- 
sistance and  then  through  the  primary  winding  the  other  end  of  the 
primary  winding  being  connected  to  the  timer.  From  the  timer  the 
current  flows  back  to  a  terminal  on  the  coil  housing,  this  being  con- 
nected to  one  side  of  the  condenser  the  other  side  of  which  is  connected 
to  the  end  of  the  primary  leading  to  the  timer.  From  this  binding 
post  the  current  is  lead  back  to  the  switch  where  it  is  grounded. 
When  the  switch  is  turned  "off"  and  then  "on"  again  the  current 


W) 

E 


167 


168  MOTOR  VEHICLES  AND  THEIR  ENGINES 

takes  the  same  path  but  flows  in  the  opposite  direction.  This  is 
accomplished  by  the  switch  for  in  one  position  the  lead  from  the  coil 
is  connected  to  the  battery  terminal  and  the  lead  from  the  timer  is 
grounded.  In  the  other  position  of  the  switch  these  connections  are 
reversed. 

As  the  current  passes  through  the  primary  of  the  coil  in  a  different 
direction  every  time  the  engine  is  operated  it  eliminates  the  pos- 
sibility of  the  soft  iron  core  becoming  magnetized  thus  weakening 
the  strength  of  the  induced  current.  It  also  prevents  excessive  wear 
on  one  of  the  contact  points. 

REMY  IGNITION  SYSTEM 

This  system  consists  of  two  units  mounted  on  one  bracket,  the 
coil  assembly  and  the  timer-distributor  assembly  (Fig.  136).  Both 
ends  of  the  primary  winding  are  led  to  binding  posts  on  the  top  of  the 
coil  housing,  one  of  these  being  connected  to  the  battery  and  the 
other  to  the  tuner.  One  end  of  the  secondary  is  internally  grounded 
the  other  being  lead  out  to  a  binding  post  on  the  side  of  coil  housing. 
The  condenser  is  contained  in  the  timer  housing,  one  side  being 
grounded  and  the  other  connected  to  the  primary  lead  wire  at  the 
tuner.  This  coil  may  or  may  not  be  equipped  with  a  resistance  to 
reduce  the  amount  of  current  flowing  through  the  primary. 

The  timer  is  of  the  construction  used  for  saturated  coils.  Only 
one  of  the  contacts  is  insulated  the  other  being  internally  grounded. 

The  distributor  is  of  the  raised  segment  type  with  a  metal  contact 
segment  on  the  rotor.  It  is  superimposed  on  the  timer  cam  and  is 
driven  by  the  same  shaft.  Advanced  and  retarded  ignition  are 
accomplished  by  manual  control  in  the  usual  manner  by  turning  the 
timer-distributor  housing. 

This  is  a  typical  one-wire  system  using  a  ground  return.  Fig.  137 
shows  a  wiring  diagram  of  the  internal  connections. 

ATWATER-KENT  SYSTEM 

This  system  consists  of  two  separate  self-contained  units,  the 
coil  assembly  and  the  time-distributor  assembly  with  automatic 
spark  advance. 

The  coil  is  usually  placed  on  the  dash  and  is  wound  for  6  volts. 
Both  ends  of  the  primary  and  secondary  windings  are  brought  out 
to  binding  posts  on  the  coil  box. 

The  timer  is  so  constructed  that  the  coil  is  non-saturated  thus 
reducing  the  current  consumption.  Both  contacts  are  insulated 


BATTERY  IGNITION  SYSTEMS 


169 


Secondary  Cable   •- 


.•Leads  h  Plugs 


'Distributor  Cover 


Oiler 


;  Drive  Shaft 


Fits  Standard 
Magneto  Base  Bracket"" ' 


Oilers 


Fig.  136— Unit  Assembly 


,^^ 


Fig.  137 — Internal  Wiring  Diagram 


170 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


and  the  condenser  is  connected  in  parallel  with  them  and  enclosed 
in  the  timer  housing. 

The  distributor  is  of  the  raised  segment  type  having  a  metal 
segment  on  the  rotor  which  is  superimposed  on  the  timer  cam  and 
driven  by  the  same  shaft. 

Both  manual  and  automatic  spark  advance  are  employed  in  this 
system  each  being  independent  of  the  other.  The  manual  control 
moves  the  housing  carrying  the  contact  points  and  is  controlled  from 


Fig.  138 — Automatic  Advance  Mechanism 

the  steering  wheel.  The  automatic  advance  is  of  centrifugal  con- 
struction (Fig.  138)  advancing  the  position  of  the  cam  with  respect 
to  the  rotation  of  the  shaft  as  the  speed  increases. 

Fig.  139  shows  a  wiring  diagram  of  the  internal  connections  of 
this  system.  One  side  of  the  battery  "K"  is  connected  to  "C"  while 
the  other  is  connected  to  terminal  "B"  of  the  switch.  Terminal 
"A"  is  connected  to  one  side  of  the  primary  winding  while  "D"  is 
connected  to  one  of  the  timer  contacts.  The  other  side  of  the  primary 
winding  is  connected  to  the  remaining  timer  contact.  One  side  of 
the  secondary  winding  is  grounded  and  the  other  connected  to  the 
central  distributor  terminal.  The  current  flows  through  the  primary 
circuit  in  either  direction  depending  upon  the  position  of  the  switch. 
When  in  the  position  as  shown  by  the  heavy  lines  the  current  passes 
from  the  battery  through  the  primary  winding  to  the  timer  and  back 
through  the  switch  to  the  battery.  When  the  switch  is  in  the 
position  shown  by  the  dotted  lines  the  current  flows  to  the  timer 
and  through  the  primary  in  the  opposite  direction.  This  prevents 
residual  magnetism  in  the  core  and  excessive  wearing  away  of  one 
contact. 


BATTERY  IGNITION  SYSTEMS 


171 


Fig.  139— Internal  Wiring  Diagram 

Practically  all  makes  of  Battery  Ignition  Systems  of  the  non- 
vibrating  type  are  like  one  of  those  just  described.  The  saturated 
coil  is  nearly  always  used  and  the  reverse  current  switch  is  quite 
common.  The  tendency  now  seems  to  be  toward  placing  the  con-- 
denser in  the  timer  housing  rather  than  placing  it  inside  the  coil 
housing  where  it  is  hard  to  get  at.  The  combined  timer-distributor 
is  used  almost  without  exception  and  a  compact  unit  with  short 
direct  connections  is  the  predominating  construction.  The  recent 
wide  adoption  of  battery  ignition  systems  has  resulted  in  many 
improvements  and  excellent  results  are  obtained. 


CHAPTER  XVII 


MAGNETOS 
ARMATURE  TYPE 

Before  electrical  generators  were  used  on  motor  vehicles  a  great 
deal  of  trouble  was  experienced  with  battery  ignition  systems  since 
the  source  of  current  was  not  always  dependable.  If  the  battery 
was  composed  of  dry  cells  it  was  effected  by  dampness  and  was  short- 
lived. If  a  storage  battery  was  used  the  machine  was  put  out 
of  operation  every  time  it  became  necessary  to  recharge  the  battery. 
This  resulted  in  constant  trouble  and  annoyance. 

To  eliminate  this  unreliability  the  magneto  was  developed  and 
the  high  tension  magneto  has  been  adopted  for  ignition,  since  it  is 
more  reliable,  being  a  self-contained  unit.  The  efficiency  of  operation 
of  the  battery  ignition  system  depends  upon  the  current  flowing 
through  the  primary  winding  and  the  rapidity  of  collapse  of  the  field. 
Difficulties  are  encountered  due  to  additional  resistance  in  the  primary 
circuit  or  the  reduction  of  the  battery  voltage.  These  difficulties 
are  not  experienced  with  the  magneto  as  all  connections  are  internally 
made  and  an  outside  source  of  current  is  not  depended  upon  to 
magnetize  the  core. 

The  iron  core  of  the  spark  coil  is  magnetized  by  current  by  some 
outside  source  such  as  a  battery.  The  magneto  eliminates  this,  the 
armature  core  becoming  magnetized  by  being  placed  between  the  oppo- 
site poles  of  strong  permanent  magnets  so  that  it  forms  a  part  of  a  com- 
pound magnetic  circuit.  The  armature  core  is  of  the  socalled  "  shuttle" 

or  "anchor"  type  and  is  mounted  upon  a 
horizontal  axis  so  that  it  can  be  revolved 
between  the  pole  shoes  of  the  permanent 
horseshoe  magnets  (Fig.  140).  It  is  so 
shaped  that  wire  may  be  wound  upon  it. 
The  air  gaps  across  which  the  magnetic 
lines  of  force  must  flow  are  made  as  short 
as  possible.  The  bearings  upon  which 
the  armature  shaft  is  mounted  must  be 
in  good  condition  since  proper  results  will 
not  be  obtained  if  the  armature  core  is 
allowed  to  rub  either  of  the  pole  shoes. 

172 


Fig.  140 — Armature  in 
Place  Between  Magnets 


(d) 


(9) 


(*)  (I) 

Fig.  141 — Change  of  Magnetic  Flux  in  Revolving  Armature 

173 


174 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


Fig.  141  shows  several  positions  of  the  armature  core  of  a  magneto 
with  relation  to  the  pole  shoes  during  one  revolution.  Starting  with 
the  armature  core  at  position  A  all  the  lines  of  force  flow  in  at  "H" 
and  through  the  core  neck  in  passing  from  the  north  to  the  south 
poles  of  the  horseshoe  magnets.  If  the  core  is  revolved  clockwise 
as  indicated  by  the  arrow,  it  will  next  reach  the  position  B  and  fewer 
lines  of  magnetic  force  will  flow  through  the  core  neck  since  less  of 
the  curved  sides  of  the  core  are  now  opposite  the  pole  pieces.  When 
the  core  has  revolved  to  position  C  still  less  of  the  curved  portion  is 
opposite  the  pole  pieces  and  the  number  of  lines  of  force  passing 
through  the  core  neck  is  still  further  decreased.  When  the  core  has 
reached  vertical  position  D  all  the  lines  of  force  flow  through  the 
curved  sides  and  none  through  the  neck  of  the  armature  core.  The 
reason  for  this  is  because  the  magnetic  lines  of  force  take  the  path 
offering  the  least  resistance.  As  the  armature  core  is  revolved  to 
position  E  a  few  lines  of  force  start  to  flow  through  the  core  neck 
again  but  in  the  opposite  direction  leaving  it  at  "H."  As  the  arma- 
ture core  is  revolved  through  the  position  F  the  number  of  lines  of 
force  flowing  through  the  core  neck  increases  until  it  reaches  a 
maximum  when  the  core  is  revolved  to  the  position  G.  During  the 
next  half  revolution  as  the  armature  revolves  through  positions  H 

to  L  exactly  the  same  changes  of 
magnetic  flux  take  place  through 
the  core  neck  as  during  the  first 
half  revolution. 

When  the  armature  core  is 
rotated  at  a  uniform  speed  the 
magnetic  flux  flowing  through  the 
core  neck  changes  from  a  maxi- 
mum at  A  to  zero  at  D,  to  a 
maximum  in  the  reversed  direc- 
tion at  G,  and  to  zero  at  J  or 
from  a  maximum  to  zero  twice 
during  one  revolution.  The  rate 
of  change  is  not  uniform  and  is 
greatest  as  the  armature  core 
approaches  the  vertical  position. 
This  is  shown  graphically  in 
Fig.  142. 

Fig.  142— Curve  Showing  Flux  Varia-       If  a  Primary  and  secondary 
tions  During  One-half  Revolution     winding  is  wound  on  a  soft  iron 


MAGNETOS,  ARMATURE  TYPE  175 

ring  (Fig.  143)  and  the  amount  of  current  flowing  through  the  primary 
is  varied  the  magnetic  flux  flowing  around  through  the  iron  ring  will 
be  varied  accordingly.  When  the  number  of  lines  of  magnetic  force 
threading  through  the  secondary  is 
changed  a  current  will  be  induced  in  it. 
The  more  rapid  the  rate  of  change  the 
greater  will  be  the  induced  voltage.  This 
electrical  principle  of  induction  is  ex- 
pressed in  Faraday's  Law  and  is  stated 
as  follows:  "The  induced  E.  M.  F.  is 
proportional  to  the  rate  of  change  of  theFig'  l«-*nv  Transformer 
magnetic  lines  of  force  or  flux  threading  through  a  coil."  This 
principle  is  employed  in  the  operation  of  a  magneto  since  the  mag- 
netic flux  flowing  through  the  armature  core,  about  which  the 
conductors  are  wound,  varies  in  intensity. 

If  a  coil  of  insulated  wire  is  now  wound  about  the  armature  core 
neck  (Fig.  141)  to  form  a  complete  circuit,  current  will  be  induced  in 
the  winding  when  the  armature  is  revolved  between  the  pole  pieces. 
This  is  due  to  the  change  in  magnetic  flux  through  the  armature  core. 
The  induced  voltage  will  be  proportional,  or  nearly  so,  to  the  rate  of 
change  of  the  magnetic  flux  through  it.  In  Fig.  144  a  complete 
electric  circuit  is  obtained  by  grounding  both  ends  of  the  insulated 
wire  to  the  core.  These  connections  are  indicated  by  black  spots 
"l"and"2." 

When  the  armature  is  at  A  (Fig.  144)  it  is  in  one  of  the  positions 
where  the  flux  is  a  maximum.'  through  the  armature  core  neck.  As 
the  armature  revolves  through  the  first  quarter  revolution  from  posi- 
tion A  to  D  the  magnetic  flux  through  the  core  neck  decreases, 
slowly  at  first  but  at  an  increasing  rate  until  position  D  is  reached. 
The  decrease  of  magnetic  flux  through  the  core  neck  causes  an 
induced  electric  current  to  flow  as  indicated  through  the  insulated 
wire  of  the  winding.  The  path  of  the  current  is  from  "2"  through 
the  insulated  wire  to  "  1 "  and  thence  through  the  metal  of  the  core 
from  "  1 "  to  "2."  The  current  flow  beginning  at  zero  keeps  increas- 
ing during  the  first  quarter  revolution  and  reaches  its  maximum  at 
position  D  of  the  armature.  As  the  armature  is  revolved  from 
position  D  the  current  decreases  in  value  until  it  drops  to  zero  again 
when  the  armature  has  reached  position  G.  During  the  second  half 
revolution  from  G  to  L  similar  variations  in  the  current  take  place 
but  the  current  now  flows  from  "1"  toward  "2"  since  the  direction 
of  the  magnetic  flux  through  the  core  neck  has  been  reversed. 

Starting  from  position  A  the  current  increases  from  zero  to  a 
maximum  at  D  and  back  to  zero  again  at  G.  It  then  increases  in  the 


Fig.  144 — Electro-magnetic  Induction  in  Primary  Circuit 

176 


MAGNETOS,  ARMATURE  TYPE 


177 


opposite  direction  to  a  maximum  at  J  and  back  to  zero  again  at  A. 
An  electric  current  of  the  kind  just  described  is  called  an  alternating 
current. 

The  induced  current  in  the  primary  winding  depends  upon  the 
rate  of  change  of  flux  through  the  armature  core  neck.  If  the  speed 
of  rotation  of  the  armature  is  increased  the  rate  of  change  will  be 
proportionately  increased.  Therefore,  the  induced  voltage  depends 
upon  the  speed  at  which  the  magneto  is  driven. 

In  order  to  start  an  engine  on  magneto  sufficient  speed  of  rotation 
must  be  attained  to  produce  current  in  the  primary.  If  a  powerful 
engine  is  cranked  by  hand,  especially  a  heavy  duty  type  such  as  is 
used  on  tractors,  sufficient  speed  will  not  be  attained  to  produce 
the  desired  current.  This  difficulty  is  overcome  by  the  use  of  an 
impulse  starting  device  (Fig.  145). 

It  is  so  designed  that  a  catch  holds  the  magneto  armature  (or 
rotor)  during  80  degrees  of  travel  and  then  is  tripped  throwing  the 


Fig.  145 — Impulse  Starter 

armature  ahead  at  the  rate  of  approximately  500  R.  P.  M.  by  means 
of  a  coil  spring,  assuring  a  good  spark  properly  timed  with  the  engine. 
By  pressing  down  on  the  back  end  of  ratchet  catch  lock  "TS-8," 
ratchet  catch  "TS-11"  will  be  released.  This  allows  it  to  engage 
with  the  notch  on  ratchet  "TS-4,"  which  is  keyed  to  the  armature, 
holding  it  stationary  while  case  "TS-1"  turns  through  80  degrees  com- 
pressing the  coil  spring  "TS-23."  When  the  lug  on  case  "TS-1" 
revolves  far  enough  to  lift  catch  "TS-11,"  the  armature  is  thrown 
ahead  with  a  rush  by  the  compressed  spring.  This  produces  the 
desired  induced  current  even  though  the  engi^  is  being  turned  over 
slowly.  The  armature  when  released  is  thrown  to  position  D  (Fig. 
141)  so  that  it  passes  quickly  through  the  point  where  the  maximum 
rate  of  change  of  flux  takes  place.  The  same  thing  takes  place 
during  the  second  half-revolution  of  the  armature. 

When  the  armature  is  in  positions  A  and  G  (Fig.  141)  it  accom- 
modates itself  to  the  greatest  number  of  lines  of  force  and,  there- 


178  MOTOR  VEHICLES  AND  THEIR  ENGINES 

fore,  resists  being  turned  from  these  positions.  If  a  flexible  shaft 
coupling  is  provided  the  armature  will  lag  behind  the  shaft  causing 
tension  in  the  coupling.  When  the  tension  has  become  sufficient 
the  armature  will  be  forced  to  rotate.  The  stored-up  energy  then 
turns  the  armature  with  increasing  speed  causing  it  to  catch  up  with 
the  shaft.  This  results  in  the  armature  rotating  through  the  vertical 
position  at  a  rate  exceeding  the  speed  of  the  shaft,  thus  increasing 
the  induced  voltage.  For  this  reason  flexible  couplings  are  ad- 
vantageous and  often  used. 

The  voltage  induced  in  a  single  winding  on  a  revolving  armature 
core  will  not  be  sufficiently  high  (approximately  200  volts)  to  jump 
a  fixed  air  gap  and  for  this  reason  a  magneto  of  such  construction  is 
called  a  low  tension  magneto.  It  is  still  necessary  to  send  the  cur- 
rent through  a  spark  coil  in  order  to  obtain  sufficient  voltage  for 
ignition  purposes;  hence,  all  the  parts  of  the  battery  ignition  system 
remain  except  the  battery  which  has  now  been  replaced  by  a  low 
tension  magneto.  This  arrangement  will  still  be  found  in  a  few 
ignition  systems  used  for  motor-propelled  vehicles. 

High-voltage  current  can  be  obtained  directly  from  the  magneto 
by  the  addition  of  a  secondary  winding.  This  is  wound  on  top  of  the 
primary  winding  on  the  armature  core  just  as  the  secondary  of  a 
spark  coil  is  wound  on  top  of  its  primary  winding.  As  the  armature 
is  revolved  current  is  built  up  in  the  primary  winding  due  to  the 
rapid  change  of  magnetic  flux  through  the  armature  core.  This 
current  reaches  a  maximum  when  the  armature  has  reached  ap- 
proximately a  vertical  position  D  or  J  (Fig.  144).  During  the  same 
part  of  a  revolution  current  is  also  induced  in  the  secondary  winding 
but  the  voltage  is  not  sufficiently  high  to  cause  a  spark  to  jump  an 
air  gap.  If  the  primary  circuit  is  suddenly  broken  as  the  armature 
moves  just  beyond  these  positions  the  magnetic  field  set  up  by  the 
current  flowing  through  the  primary  will  be  broken  down.  Just  as 
in  the  spark  coil  this  induces  a  current  of  high  voltage  in  the  secondary 
(approximately  5000  volts)  which  will  jump  a  fixed  air  gap. 

Since  it  is  necessary  for  the  primary  circuit  to  be  broken  at  certain 
definite  positions  of  the  armature  an  interrupter  is  used  driven  by 
the  armature  shaft.  Li  this  way  the  rotation  of  the  armature  and 
interrupter  are  kept  perfectly  synchronized. 

Fig.  146  shows  all  the  necessary  parts  of  a  high  tension  magneto 
and  diagrammatically  illustrates  how  they  should  be  connected. 
The  interrupter  on  a  magneto  will  normally  have  two  cams  since  the 
primary  circuit  can  ordinarily  be  broken  but  twice  during  one  revolu- 
tion. This  is  because  there  are  but  two  positions  of  the  armature  in 


MAGNETOS,  ARMATURE  TYPE 


179 


I '^Ground' 

Fig.  146 — Typical  Wiring  Diagram  of  High  Tension  Magneto 

common  constructions  of  magnetos  at  which  the  induced  primary 
current  is  at  a  maximum. 

A  condenser  is  connected  in  parallel  with  the  breaker  points  to 
prevent  arcing  and  is  generally  mounted  in  the  end  of  the  armature, 
revolving  with  it. 

A  switch  is  provided  which  will  continuously  ground  the  primary 
circuit  when  closed.  This  prevents  the  interrupter  from  interrupting 
the  primary  circuit  consequently  preventing  a  current  of  high  voltage 
from  being  induced  in  the  secondary.  By  closing  this  switch  the 
ignition  is  "shut  off." 

One  end  of  the  secondary  is  grounded  through  the  primary,  while 
the  other  is  connected  to  a  distributor  just  as  was  done  in  a  battery 
ignition  system.  The  same  types  of  distributors  are  found  on  mag- 
netos as  are  used  on  battery  ignition  systems,  there  being  as  many 
contact  segments  as  there  are  cylinders.  For  this  reason  the  dis- 
tributor will  always  be  internally  geared  so  as  to  run  at  one-half  engine 
speed  (on  four-cycle  engines). 

The  ordinary  construction  of  magneto  with  "shuttle"  type  of 
armature  produces  two  sparks  during  each  revolution  equally  spaced 
or  180  degrees  apart.  This  is  because  there  are  but  two  points  where 
the  rate  of  change  of  magnetic  flux  through  the  armature  is  greatest. 
When  magneto  ignition  is  used  for  twin-cylinder  motor-cycles  with 
"V"  type  cylinders  a  special  construction  is  necessary  to  obtain 
two  sparks  not  equally  spaced.  This  is  required  because  the  cylinders 
are  set_at  an  angle  varying  from  42  degrees  to  47  degrees,  depending 


180 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


upon  the  manufacturer.  Assuming  the  angle  is  45  degrees,  No.  2 
cylinder  fires  315  degrees  of  engine  revolution  after  No.  1  while  the 
engine  turns  through  405  degrees  of  revolution  after  No.  2  fires  before 
No^l  fires  again.  Since  the  magneto  gives  two  sparks  per  revolution 
it  is  driven  at  half  engine  speed,  therefore,  the  sparks  it  delivers  must 
be  spaced  157J/£  degrees  and  202^  degrees  of  magneto  revolution 
apart.  This  is  accomplished  by  advancing  the  second  spark  (nor- 
mally occurring  180  degrees  after  the  first  spark)  22^  degrees.  This 
is  done  by  moving  the  point  of  maximum  change  of  flux  ahead  a 
similar  amount.  Since  the  relative  positions  of  pole  shoes  and 
armature  determines  this  point  the  desired  result  may  be  obtained 
by  altering  the  shape  of  the  pole  shoes  and  armature. 

Fig.  147  shows  the  pole  shoes 
and  armature  of  the  Bosch  Mag- 
neto designed  for  twin-cylinder 
motor-cycle  ignition.  The  tips 
of  the  diagonally  opposite  halves 
of  each  pole  shoe  are  cut  away 
and  opposite  sides  of  each  half 
of  the  armature  core  are  almost 
Fig.  147— Bosch  Pole  Shoes  and  entirely  removed. 

Armature  for  Motor  Cycles  when  ^  armature  core  ig  in 

the  position  shown  at  A  (Fig.  148)  the  lines  of  force  flow  from  the 
north  pole  across  the  small  air  gap  "A"  and  through  the  core  dia- 
gonally. They  enter  the  south  pole  by  flowing  across  the  similarly 
small  air  gap  "A"  at  the  opposite  (far)  end  of  the  armature  core. 
They  do  not  pass  straight  through  the  armature  core  because  the 
large  air  gaps  "B"  offer  a  much  harder  path. 

The  point  of  maximum  current  B  in  the  primary  will  be  when 
the  armature  has  just  cleared  the  trailing  pole  tips  "C"  and  "D" 
as  in  the  usual  construction. 

When  the  armature  core  has  reached  the  position  C  the  lines  of 
force  flow  from  the  cut  away  part  of  the  north  pole  shoe  across  the 
small  air  gap  "A"  diagonally  through  the  armature  core.  They  then 
pass  into  the  cut  away  south  pole  shoe  by  flowing  across  the  similarly 
small  air  gap  "A"  at  the  opposite  (near)  end  of  the  armature  core. 
They  do  not  pass  straight  through  the  armature  because  of  the  large 
air  gaps  "B." 

The  second  point  of  maximum  induced  current  in  the  primary  will 
be  when  the  armature  has  just  cleared  the  cut-away  trailing  pole 
shoe  tips  at  "E"  and  "F."  In  this  case,  however,  the  impulse  of 
current  will  come  earlier  with  respect  to  the  movement  of  the  arma- 
ture than  in  the  first  case  by  the  amount  that  the  pole  tips  are  cut 


MAGNETOS,  ARMATURE  TYPE 


181 


away.    This  amount  may  be  varied  and  in  the  case  just  considered 
would  have  to  be  equivalent  to  22J/2  degrees  of  armature  rotation. 


Fig.  148 — Change  of  Magnetic  Flux  in  Motor  Cycle  Magneto  Armature 

Thus  the  second  spark  is  moved  up  22J/£  degrees  nearer  the  first 
spark  which  is  the  proper  amount  for  a  45-degree  "V"  type  twin- 
cylinder  engine. 

Other  methods  of  producing  this  same  result  have  been  devised 
with  varying  degrees  of  success.  One  common  construction  is  to 
cover  part  of  the  pole  shoes  with  brass  which  cuts  off  the  lines  of 
force  emanating  from  that  particular  part.  Another  is  to  cut  a  narrow 
groove  in  the  pole  shoes  which  produces  almost  the  same  effect  when 
the  armature  leaves  the  edge  of  the  groove  as  when  it  leaves  the  pole 
shoe  tip.  Fig.  149  shows  this  construction  employed  in  the  Berling 
Magneto.  In  this  way  impulses  of  induced  current  are  obtained  at 
two  different  points,  the  primary  being  broken  first  at  one  and  then 


182 


MOTOR^VEHICLES  AND  THEIR  ENGINES 


at  the  other.  The  distance  between  the  grooves  in  the  pole  shoes  and 
the  pole  shoe  tips  depends  upon  the  angle  be- 
tween the  cylinders  of  the  engine. 

BOSCH  MAGNETOS 


Bosch  magnetos  are  manufactured  in  many 
types  and  are  designated  by  a  combination  of 
letters  and  numbers  engraved  on  the  base  plate  of 
the  magneto.  The  letters  represent  the  general 
construction,  the  number  specifying  the  engine 
with  which  the  magneto  is  to  be  used.  For  ex- 
ample: Du4,  the  letters  represent  the  type  and 
the  "4"  specifies  that  it  is  for  a  four-cylinder 
engine.  A  few  of  the  typical  constructions  will  be 


Fig.  IW—Berling 

Construction  for 

Motor  Cycles 


explained  so  as  to  gain  a  general  knowledge  of  these  types  of  mag 
netos.    The  principle  upon  which  they  are  constructed  is  the  same 
as  any  shuttle  type  of  armature. 

The  most  common  types  in  use  are  the  "Du"  magnetos  con- 
structed for  engines  of  from  one  to  six  cylinders.  The  four-cylinder 
design  is  shown  in  Fig.  150.  The  six-cylinder  type  differs  only  in 


Fig.  150 — Bosch  Du4  Magneto 

that  it  has  a  distributor  arranged  with  six  segments  and  terminals 
and  the  internal  gearing  so  arranged  that  the  distributor  is  driven 
at  half  engine  speed  when  the  magneto  is  properly  installed  on  the 
engine. 

Fig.  151  shows  a  cross  section  of  this  magneto  and  the  solid  black 
represents  insulating  material.  Fig.  152  shows  the  wiring  of  the 
magneto  and  in  explaining  the  path  of  the  primary  and  secondary 


MAGNETOS,  ARMATURE  TYPE 


183 


1    116  u    2      117 


Fig.  151— Cross-section  of  Bosch  Magneto 


S  3  4 


Fig.  152 — Internal  Wiring  of  Bosch  Magneto 


184  MOTOR  VEHICLES  AND  THEIR  ENGINES 

circuits  the  numbers  of  the  parts  in  Fig.  151  will  be  used  to  give  a 
clear  conception  of  the  path  the  current  takes. 

PRIMARY  CIRCUIT. — One  end  of  the  primary  winding  which 
consists  of  a  few  turns  of  heavy  wire  is  in  metallic  connection  with 
the  armature  core.  The  other  end  is  connected  to  the  condenser 
plate  "1."  The  interrupter  fastening  screw  "2"  which  screws  into 
plate  "1"  conducts  the  primary  current  to  the  insulated  contact 
block  supporting  the  long  platinum  screw  "G-2"  of  the  magneto 
interrupter.  The  interrupter  lever  carrying  the  short  platinum 
contact  "G-3"  is  mounted  on  the  interrupter  disc  which  is  elec- 
trically connected  to  the  armature  core.  The  primary  circuit  is 
complete  when  the  two  platinum  points  are  brought  together  and 
interrupted  whenever  these  points  are  separated.  The  separation 
of  the  platinum  points  is  controlled  by  the  action  of  the  interrupter 
lever  as  it  bears  against  the  steel  segments  screwed  to  the  inner 
surface  of  the  interrupter  housing  (timing  lever  housing).  There 
are  two  segments  in  this  housing  so  that  the  circuit  is  broken  at  the 
two  points  of  maximum  current  in  the  primary.  The  condenser 
"9"  is  connected  acorss  the  interrupter  points  so  as  to  stop  the 
arcing.  One  side  is  connected  to  the  condenser  plate  "1"  and  the 
other  side  is  connected  to  the  armature  core. 

SECONDARY  CIRCUIT.— The  secondary  winding  is  composed 
of  a  great  number  of  turns  of  fine  wire.  One  end  is  connected  to  the 
primary  and  the  other  end  to  the  insulated  current  collector  ring 
(slip-ring)  "10"  mounted  on  the  armature  at  the  driven  end.  The 
slip  ring  is  made  of  insulated  material  with  a  continuous  brass  seg- 
ment inserted.  In  contact  with  this  segment  is  the  carbon  brush 
"  11 "  held  by  the  carbon  holder  "  12."  On  top  of  the  carbon  holder 
there  is  a  terminal  "  13  "  from  which  the  current  is  conducted  by  the 
insulating  bar  "14"  to  the  brass  segment  "18"  in  the  center  of  the 
distributor.  A  brush  holder  "  15  "  is  mounted  on  a  gear  which  meshes 
with  a  gear  on  the  armature  shaft  so  that  the  operation  of  the  dis- 
tributor will  be  in  perfect  ^synchronism  with  the  armature.  Carbon 
holder  "15"  contains  a  carbon  brush  "16"  which  conducts  the  cur- 
rent from  the  brass  segment  "18"  to  the  segments  which  are  em- 
bedded in  the  distributor  plate  "17."  These  segments  are  connected 
with  the  terminal  studs  on  the  face  of  the  distributor  plate  and  the  lat- 
ter are  connected  by  cables  to  the  spark  plugs  in  the  various  cylinders. 
In  the  cylinders  the  high  tension  current  produces  a  spark  and  the 
current  then  returns  through  the  engine  to  the  magneto  armature 


MAGNETOS,  ARMATURE  TYPE  185 


core,  completing  the  secondary  circuit.  To  protect  the  armature 
and  other  current  carrying  parts  a  safety  spark  gap  "K"  is  provided, 
connected  between  the  terminal  "13"  and  dust  cover  "22."  This 
gap  is  so  arranged  as  to  have  more  resistance  than  the  gap  at  the 
spark  plug  under  compression.  Under  ordinary  conditions  the  cur- 
rent will  flow  through  its  normal  path  but  if  for  any  reason  the 
resistance  in  the  secondary  circuit  is  increased  to  a  high  point,  as 
when  a  cable  becomes  disconnected  or  the  gap  is  too  wide  at  the 
spark  plugs,  the  high  tension  current  will  discharge  across  the  safety 
spark  gap.  In  this  way  the  possibility  of  breaking  down  the  in- 
sulating material  of  the  instrument  itself  will  be  eliminated. 

CUTTING  OUT  THE  IGNITION.— Since  high  tension  current 
is  generated  only  on  the  interruption  of  the  primary  circuit,  it  is 
evident  that  in  order  to  cut  out  the  ignition  it  is  necessary  merely  to 
divert  the  primary  current  to  a  path  which  is  not  effected  by  the 
action  of  the  magneto  interrupter.  This  is  accomplished  as  follows: 
Spring  "118"  being  in  contact  with  screw  "2"  leads  the  current  to 
the  insulated  binding  post  "24"  and  if  this  binding  post  is  connected 
to  a  switch  having  the  other  side  grounded  the  primary  in  the  mag- 
neto will  be  grounded  at  both  ends  when  the  switch  is  closed.  There- 
fore, the  operation  of  the  interrupter  will  not  break  down  the  current 
flowing  through  it  and  consequently  there  will  be  no  secondary 
current. 

The  ZR  type  of  magneto  is  arranged  for  four  and  six-cylinder 
engines  and  is  identical  in  operation  with  that  of  the  Du4  and  the 
path  of  the  current  is  identically  the  same.  It  differs  in  that  it  is 
a  water-tight  construction.  When  speaking  of  water-tight  magnetos 
it  is  to  be  borne  in  mind  that  this  does  not  imply  that  the  magneto 
can  be  submerged  in  water  for 
any  length  of  time.  It  will  with- 
stand damaging  effects  of  rain, 
moisture,  or  a  stream  of  water 
squirted  on  it  when  the  car  is 
being  washed.  This  is  accom- 
plished by  the  special  construc- 
tion of  end  plates  and  distributor 
with  special  terminal  nuts  as 
shown  in  Fig.  153.  The  edges  of 
the  oil  covers  are  bent  down  and 
felt  inserts  used.  Between  the 

magnets  there  are  strips  of  paper 

f  -  ,,  Fig.  153— Bosch  ZR6  Magneto 

and  felt  washers. 


186 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


Fig.  154 — ZR4  Magneto  Partially  Disassembled 


Fig.  154  shows  the  distributor  and  timing  lever  removed  from  the 
magneto  showing  carbon  brush  and  holder  on  the  distributor  gear 
wheel  as  explained  in  the  Du4  construction. 

The  LT4  type  magneto  is  designed  for  four  cylinder  engines.  It 
is  in  reality  a  modified  ZR4  magneto,  all  electrical  circuits  being 
identical  and  water-proof  construction  being  used.  This  type  was 
especially  designed  for  the  Government,  a  distributor  adopted  as 
"standard"  being  employed.  Other  dimensions,  such  as  height 
of  shaft,  taper  of  shaft,  and  dimensions  of  base  platejare  in 
accordance  with  Government  specifications.  This  standardization 
permits  of  interchangeability  of  magnetos  on  Government  apparatus 
regardless  of  manufacture,  without  tools  or  special  equipment  being 
used.  This  is  of  great  assistance  in  the  field,  since  a  very  quick  change 
can  be  made  and  the  necessity  of  carrying  as  spare  equipment  extra 
magnetos  of  each  make  is  eliminated.  Fig.  155  shows  this  magneto 
with  the  distributor  and  timer  lever  cover  removed. 

The  ZEV  type  of  magneto  (Fig.  156)  is  for  a  twin  cylinder  motor- 
cycle engine  and  is  a  water-tight  construction.  As  this  magneto  is 
used  for  motor-cycles  which  require  the  spark  to  occur  at  unequal 
intervals.  The  pole  shoes  and  armature  are  cut  away  as  previously 
explained.  In  every  other  respect  the  magneto  is  identical  with  the 
other  Bosch  Magnetos.  In  Fig.  156  the  interrupter  cover  is  removed 
showing  that  the  cams  are  not  set  an  equal  distance  apart,  but  are 


MAGNETOS,  ARMATURE  TYPE 


187 


170 


263 


205(11) 


Fig.  155 — Bosch  Magneto  Standardized  for  Military  Purposes 

arranged  to  interrupt  the  circuit  at  the  proper  time  to  compensate 
for  the  cylinders  being  set  at  an  angle. 
The  primary  circuit  in  this  mag- 
neto is  the  same  as  in  all  other  Bosch 
Magnetos.  The  secondary  circuit  is 
slightly  different.  One  end  of  the 
secondary  is  grounded  through  the 
primary  winding  and  the  other  end  is 
connected  to  the  segment  of  the  slip 
ring.  The  slip  ring  in  this  type  has  a 
short  segment  instead  of  one  that  is 
continuous.  In  contact  with  this  slip 
ring  are  two  carbon  brushes  and 
holders  which  are  placed  one  on  each 
side  of  the  magneto.  In  this  manner 
the  segment  of  the  slip  ring  is  in  con- 
tact with  only  one  brush  when  the 

primary  circuit  is  interrupted  during  either  half  revolution.  Cables 
connect  the  spark  plugs  to  these  carbon  holders  so  that  the  cur- 
rent is  first  led  to  one  plug  and  then  to  the  other.  As  the  sparks 
are  not  equally  spaced  care  must  be  taken  to  connect  the  proper 
carbon  holder  to  the  spark  plug  in  No.  1  cylinder.  Fig.  157  shows 
the  proper  wiring  from  the  carbon  holders  to  the  spark  plugs  in  the 
cylinders. 


20W1) 


455  W5 

Fig.  156— Bosch  ZEV 
Magneto 


188 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


n 


Fig.  157 — Wiring  Diagram  of  a  Twin  Cylinder  Motor 
with  a  "ZEV"  Magneto 

EISEMANN  MAGNETO 

The  G-4  magneto  is  designed  for  four-cylinder  engines  and  is 
made  up  in  two  general  constructions,  Edition  I  (Fig.  158)  and 
Edition  II  (Fig.  159)  The  later  model  is  used  more  extensively 


Fig.  160 — Internal  Wiring  of  Eisemann  Magneto 

than  the  Edition  I.     Fig.  160  shows  the  internal  wiring  of  these 
magnetos. 


DISTRIBUTOR  PLATE 


CABLE  FOR  CUTTING 
OFF  IGNITION 


DISTRIBUTOR 
CARBONS 


END  CAP 


SETTING  SCREW 


DISTRIBUTOR  DISC 

CARBON  B'RUSH  PICKING  UP 
CURRENT  FROM  COLLECTOR  RING 


SETTING  MARKS 


FIBRE 
CAMS 


COPPER  BRUSH  FOR  SHORT 
CIRCUITING  IGNITION 

Fig.  158 — Eisemann  G-4  Ed  I 


DISTRIBUTOR    PLATE 

WITH 
•  AUR-PROOF   CABLE    FASTENINGS 


INDICATOR  POINT 

FOR    SETTING   MAGNETO 

TO   MOTOR 


SETTING 
MARKS 


CARBON  BRUSff 

DISTRIBUTOR  *VTO  PICK  UP 

CARBON   BRUSHES    1*CURRENT  FROM 
COLLECTOR  RING 


CABLE  CONNECTION 
FOR  CUTTING  OFF 
MAGNETO   IGNITION 


WAILK-PROOF   ENt 
CAP   FOR    BREAKER 


TIMING  LEVER  BODY 


IAGNETO  CONTAC1 
BREAKER  POINTS 


Fig.  159 — Eisemann  G-4  Ed  II 


189 


190  MOTOR  VEHICLES  AND  THEIR  ENGINES 

PRIMARY  CIRCUIT.— One  end  of  the  primary  is  metallicall: 
connected  to  the  core  and  the  other  end  is  brought  out  and  splicec 
to  a  piece  of  cable.    One  end  of  the  cable  leads  to  the  condensei 
which  is  installed  at  the  driven  end  of  the  magneto  in  the  armatui 
housing,  the  other  end  being  connected  to  the  insulated  terming 
block  "J"  carrying  the  adjustable  long  platinum  screw.     In  contacl 
with  this  there  is  a  short  platinum  stud  which  is  attached  to  a  spring 
fastened  in  a  post  which  is  grounded  by  the  carbon  brush  "CB." 
This  makes  a  metallic  return  to  the  armature  core  of  the  primary 
circuit.    When  the  platinum  points  are  closed  the  circuit  is  made 
and  when  the  platinum  points  are  separated  due  to  the  action  of  the 
cam,  the  circuit  is  broken. 

SECONDARY  CIRCUIT.— The  secondary  winding  consists  of  a 
great  number  of  turns  of  fine  wire.  One  end  is  connected  to  the 
primary  and  the  other  end  is  connected  to  an  insulated  collector  ring 
at  the  interrupter  end  of  the  magneto.  The  distributor  is  placed 
directly  above  the  slip  ring  and  has  a  carbon  brush  in  contact  with  it. 
This  carbon  brush  is  metallically  connected  to  a  carbon  brush  in  the 
center  of  the  distributor.  There  are  also  four  carbon  brushes  which 
are  connected  to  the  cables  leading  to  the  spark  plugs.  On  the 
distributor  gear  wheel  there  is  mounted  an  insulating  plate  with  a 
brass  segment  embodied  in  it.  This  gear  is  meshed  with  the  gear  on 
the  armature  shaft  so  that  they  synchronize.  The  segment  revolving 
with  the  distributor  gear  conducts  the  current  from  the  center  brush 
of  the  distributor  to  the  four  brushes  in  order.  These  carbon  brushes 
being  connected  by  cables  to  the  spark  plugs  fastened  in  the  engine 
which  is  in  metallic  connection  with  the  armature  core,  make  a 
complete  path  for  the  secondary  current. 

In  the  Edition  I  the  interruption  of  the  primary  circuit  is  accom- 
plished by  fiber  cams  inserted  in  the  timer  lever  body.  In  the  Edi- 
tion II  the  interrupter  is  of  a  different  construction  (Fig.  158).  The 
interruption  is  made  by  the  use  of  steel  segments  attached  to  the 
timer  lever  body. 

The  method  of  short-circuiting  the  primary  winding  to  put  the 
magneto  out  of  operation  is  as  follows:  A  copper  brush  in  the  end 
of  the  screw  holding  the  contact  breaker  in  place  is  metallically  con- 
nected to  the  end  cap  terminal  which,  when  connected  to  ground 
through  a  switch,  will  short-circuit  the  primary  winding.  In  the 
Edition  II  this  varies  slightly  in  that  the  carbon  brush  is  in  the  end 
cap  and  bears  against  the  interrupter  fastening  screw. 

A  few  things  to  be  noted  about  this  magneto  are  that  the  con- 
densor  is  so  installed  that  it  can  be  disconnected  without  interfering 
with  the  primary  circuit.  A  grounded  condenser  could  easily  be 


MAGNETOS,  ARMATURE  TYPE 


191 


detected  by  breaking  this  connection.  Arranging  the  slip  ring  so 
that  it  is  directly  below  the  distributor  eliminates  several  connections 
and  makes  the  instrument  more  compact.  Another  point  in  favor  of 
this  location  is  that  it  is  more  protected  than  when  located  at  the 
driven  end  of  the  magneto.  Slip  rings  located  at  the  driven  end  are 
often  broken  by  inexperienced  men  when  prying  off  gears  or  couplings. 


BERLING  MAGNETO 

Berling  Magnetos  are  manufactured  in  many  types.  The  most 
commonly  used  are  the  F-41  for  four-cylinder  engines  and  B-21  for 
twin-cylinder  motor-cycles.  Fig.  161  shows  diagrammatically  the 
internal  wiring  of  the  F-41  type. 


Fig.  161— Internal  Wiring  of  Berling  F-41 

PRIMARY  CIRCUIT.— One  end  of  the  primary  is  grounded  and 
the  other  end  is  led  to  the  condenser  plate.  The  interrupter  fastening 
screw  conducts  the  current  from  condenser  plate  to  the  insulated 
block  of  the  interrupter  carrying  one  of  the  interrupter  contacts. 
The  other  contact  is  connected  to  ground  and  completes  the  circuit 
for  the  primary  when  the  interrupter  points  are  together.  The 
separation  of  the  points  is  accomplished  by  the  lever  as  it  bears 
against  cams  pressed  in  the  surface  of  the  timing  lever  housing.  The 
condenser  is  connected  across  the  interrupter  points,  one  side  being 


192 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


connected  to  the  condenser  plate  and  the  other  to  a  wire  which  is 
grounded  to  the  armature  core. 

SECONDARY  CIRCUIT. — One  end  is  connected  to  the  primary 
to  obtain  its  ground  return,  the  other  end  is  brought  out  and  con- 
nected to  the  slip  ring.  The  slip  ring  has  a  continuous  segment  so 
that  the  brush  which  is  held  by  the  carbon  holder  is  always  in  contact 
with  it.  From  here  the  current  is  conducted  to  the  rotor  which  is 
mounted  on  the  distributor  gear  in  mesh  with  a  gear  on  the  armature 
shaft  so  that  they  are  in  synchronism.  The  distributor  is  connected 


Fig.  162— Internal  Wiring  of  Berling  B-21 

to  the  spark  plugs  by  cables;  thus  the  complete  secondary  circuit  is 
made. 

Fig.  162  shows  diagrammatically  the  internal  wiring  of  the  type 
B-21.  The  only  difference  in  this  wiring  is  that  the  slip  ring  has  a 
short  segment  instead  of  a  continuous  segment  as  in  the  F-41.  In 
contact  with  the  slip  ring  are  two  carbon  brushes  so  that  the  current 
generated  in  the  first  half  revolution  flows  to  one  carbon  brush  and 
in  the  next  half  revolution  to  the  other  brush.  Each  of  these  brushes 
must  be  connected  to  the  proper  spark  plug  as  previously  explained 
(Fig.  157). 

As  this  magneto  is  used  on  an  engine  which  has  the  cylinders 
set  at  an  angle  it  uses  a  special  construction  of  pole  shoes  and  also 
has  the  segments  in  the  interrupter  set  to  interrupt  the  circuit  at  the 
proper  time. 

The  magnetos  described  in  this  chapter  are  typical  of  all  Revolv- 
ing Armature  constructions.  Except  for  minor  details  other  mag- 
netos of  this  type  do  not  differ  from  those  explained. 


CHAPTER  XVIII 


MAGNETOS 
ROTOR  TYPE 

Ail  the  magnetos  discussed  in  the  preceding  chapter  were  con- 
structed so  that  their  windings  revolved  requiring  insulated  moving 
wires,  collector  rings,  brushes,  and  moving  contacts.  In  the  revolving 
rotor  type  the  windings  are  stationary,  the  rotor  or  inductor  revolving 
between  the  pole  pieces  of  the  magnets  conducting  the  lines  of  mag- 
netic force  through  the  soft  iron  core  about  which  the  stationary 
windings  are  placed. 


Fig.  163 — Rotor  and  Winding 

Fig.  163  shows  a  rotor  or  inductor  of  the  construction  commonly 
used  on  this  type  of  magneto.  It  consists  of  a  steel  shaft  carrying 
laminated  soft  iron  arms  fastened  to  the  shaft  and  projecting  in 
opposite  directions.  These  arms  are  shaped  so  as  to  reduce  the  air 
gap  between  them  and  the  pole  shoes  to  a  minimum  just  as  is  done 
in  the  shuttle  type  armature. 

Fig.  164  shows  several  positions  of  the  rotor  with  relation  to  the 
pole  shoes  during  one  revolution.  Starting  with  the  rotor  at  position 
A,  all  the  lines  of  force  flow  from  the  North  Pole  to  the  arm  "R," 
then  at  right  angles  through  the  shaft  and  out  through  the  other  arm 
to  the  South  Pole.  If  it  is  revolved  clockwise  it  will  next  reach 
position  B  and  fewer  lines  of  magnetic  force  will  flow  through  the 
rotor  shaft.  When  it  has  revolved  to  position  C  the  number  of 
lines  of  force  passing  through  the  rotor  shaft  is  still  further  decreased. 
When  it  has  reached  the  vertical  position  D  all  the  lines  of  force 

193 


Fig.  164 — Change  in  Flux  Through  Revolving  Rotor 

194 


MAGNETOS,  ROTOR  TYPE  195 

flow  directly  across  from  the  north  to  the  south  pole  through 
the  soft  iron  arms  and  none  flow  through  the  steel  shaft.  This  is 
because  the  magnetic  lines  of  force  take  the  path  of  least  resist- 
ance. As  the  rotor  is  revolved  to  position  E,  the  lines  of  force 
start  to  flow  through  it  again  but  in  the  opposite  direction,  leaving 
the  rotor  at  arm  "R."  As  the  rotor  is  revolved  through  the  position 
F  the  number  of  lines  of  force  flowing  through  it  increases  until  it 
reaches  a  maximum  when  the  rotor  has  reached  position  G.  During 
the  next  half  revolution  as  the  armature  revolves  through  positions 
H  to  L  the  same  changes  of  magnetic  flux  through  the  rotor  take  place 
as  during  the  first  half  revolution. 

If  the  speed  of  rotation  is  uniform  the  rate  of  change  of  magnetic 
flux  through  the  rotor  is  greatest  as  it  approaches  positions  D  and  J. 
As  already  shown  in  chapter  18  current  is  induced  in  a  winding  by 
causing  a  rapid  change  in  the  strength  of  the  magnetic  flux  threading 
through  it.  This  principle  is  applied  in  this  type  of  magneto  since 
the  necessary  varying  flux  is  obtained  by  rapidly  revolving  the  rotor. 

If  a  stationary  coil  of  insulated  wire  is  wound  about  the  steel 
rotor  shaft,  between  the  two  soft  iron  arms  as  shown  in  Fig.  163,  cur- 
rent will  be  induced  in  it  whenever  the  rotor  is  revolved.  Just  as 
in  the  revolving  armature  type  of  magneto  the  maximum  voltage 
induced  in  the  winding  will  be  when  the  rotor  has  just  passed  posi- 
tions D  and  J  (Fig.  164).  The  two  maximum  valves  will  be  equal 
but  the  flow  of  current  will  be  in  opposite  directions.  This  is  due  to 
the  reversal  of  the  direction  of  magnetic  flux  through  the  rotor. 
Hence  this  type  of  magneto  also  generates  alternating  current. 

If  but  one  winding  is  used  the  resulting  voltage  will  be  low  in 
value  and  for  that  reason  magnetos  of  this  construction  are  called 
Low  Tension  Magnetos. 

When  a  secondary  winding  is  wound  on  top  of  the  stationary 
primary  winding  high  tension  current  may  be  obtained  from  this 
type  of  magneto.  The  interrupter  is  in  the  primary  circuit  breaking 
it  when  the  rotor  is  just  beyond  the  vertical  position.  This  breaks 
down  the  field  due  to  the  current  in  the  primary  and  induces  a  high 
tension  current  in  the  secondary. 


THE  K-W  MAGNETO 

The  K-W  is  a  high  tension  magneto  of  the  inductor  type.  The 
only  revolving  part  in  this  magneto  is  the  rotor  (Fig.  165).  This 
rotor  differs  from  the  one  shown  in  Fig.  163  as  the  rotor  arms  are 
placed  at  right  angles  to  each  other  and  project  from  both  sides  of 


196 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


Fig.  165 — K-W  Rotor  and  Windings 

the  shaft.    The  same  effect  is  obtained  as  if  two  rotors  were  used, 
that  is,  four  impulses  are  induced  per  revolution  instead  of  two. 

Fig.  166  shows  how  this  is  accomplished.  The  arrows  indicate 
the  path  of  the  magnetic  flux  through  the  rotor  at  different  positions. 
It  will  be  noticed  that  the  rotor  in  this  construction  does  not  revolve 
between  the  pole  shoes  but  directly  below  them. 


ABC 
Fig.  166— Path  of  Flux  in  K-W  Magneto 


MAGNETOS,  ROTOR  TYPE 


197 


The  windings  are  stationary  and  composed  of  a  primary  and 
secondary  concentric  with  the  rotor  shaft  (Fig.  165).  The  inter- 
rupter is  wired  in  the  primary  circuit  as  usual  and  the  condenser  is 
connected  across  the  contact  points.  The  condenser  is  located  inside 
the  magnets  at  the  shaft  end  of  the  magneto.  The  interrupter 
normally  has  a  two-nosed  cam,  driven  by  the  rotor  shaft,  so  that  the 
current  is  interrupted  in  the  primary  at  but  two  of  the  four  points 
where  it  is  a  maximum.  Therefore,  it  must  be  driven  at  the  same 
speed  as  a  revolving  armature  type  of  magneto. 

The  current  from  the  secondary  passes  directly  to  the  insulated 
terminal  on  top  of  the  windings.  From  this  point  the  high  tension 
lead  conducts  it  to  the  central  terminal  of  the  distributor  which  dis- 
tributes it  to  the  various  cylinders  of  the  engine.  The  safety  spark 
gap  is  also  connected  to  this  terminal  and  is  located  just  above  the 
condenser. 


Fig.  167 — Cross-section  of  K-W.  Magneto 

Fig.  167  shows  a  cross  section  of  the  K-W  magneto,  the  various 
windings  and  connections  being  shown. 

There  are  several  K-W  magnetos,  the  models  being  designated  by 
letters  in  the  usual  manner.  When  the  letter  K  is  part  of  the  desig- 
nation it  indicates  that  the  magneto  is  equipped  with  an  impulse 
starter  such  as  already  explained  in  chapter  18. 


THE  DIXIE  MAGNETO 

The  Dixie  is  a  high  tension  magneto  of  the  inductor  type.  The 
rotor  as  usual  is  the  only  revolving  part,  but  it  differs  considerably 
in  construction  from  those  previously  described. 


198 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


Fig.  168 — Magnets  and  Rotor  of 
Dixie  Megneto 

Fig.  168  shows  the  arrangement  of  the  magnets  and  rotor.  One 
arm  of  the  rotor  always  conducts  magnetic  flux  from  the  north  pole 
of  the  magnets  while  the  other  conducts  it  to  the  south  pole.  To 
prevent  magnetic  flux  from  flowing  between  the  arms  of  the  rotor  the 
central  part  is  made  of  brass  which  is  a  non-magnetic  substance. 
The  rotor  revolves  between  pole  shoes  "F"  and  "G"  of  soft  iron 
connected  by  a  core  "C"  upon  which  the  windings  are  placed. 


Fig.  169— Path  of  Flux  in  Dixie  Magneto 

When  the  rotor  is  in  the  position  shown  at  A  (Fig.  169)  the  mag- 
netic flux  takes  the  following  path.  From  the  north  magnetic  pole 
through  the  rotor  arm  "N,"  pole  shoe  "G,"  core  "C,"  pole  shoe 
" F,"  rotor  arm  "  S,"  to  the  south  magnetic  pole.  When  the  rotor  has 
turned  to  the  position  shown  at  B,  the  path  of  the  magnetic  flux  is  as 
follows:  From  the  north  pole  of  the  magnet  through  the  rotor 


MAGNETOS,  ROTOR  TYPE  199 


arm  "N,"  to  both  pole  shoes  "F"  and  "G,"  directly  to  the  rotor 
arm  "S,"  and  thence  to  the  south  pole  of  the  magnet.  With  the 
rotor  in  this  position  none  of  the  lines  of  force  set  up  by  the  per- 
manent magnets  flow  through  the  core  "C."  When  the  rotor  has 
turned  to  the  position  shown  at  C  the  magnetic  flux  takes  the  same 
path  as  at  A  but  passes  through  the  pole  shoes  and  core  in  the  reverse 
direction.  Thus  a  rapid  change  of  flux  through  the  core  "C"  is 
obtained  which  induces  a  current  in  the  primary  winding.  This 
current  will  be  a  maximum  when  the  rotor  has  just  passed  the  vertical 
position.  If  the  primary  circuit  is  interrupted  when  the  current  is  a 
maximum,  a  current  of  high  voltage  will  be  induced  in  the  secondary. 
Since  there  are  but  two  points  at  which  the  current  is  at  a  maximum 
during  each  revolution  the  interrupter  will  have  a  two-nosed  cam 
which  gives  two  sparks  per  revolution. 


Fig.  170 — Dixie  Magneto 

Fig.  170  shows  the  waterproof  covering  and  one  magnet  removed 
from  a  Dixie  Magneto.  When  the  timing  lever  is  moved  in  advancing 
or  retarding  the  spark  the  pole  shoes  and  coil  are  moved  a  correspond- 
ing amount.  In  this  manner  the  primary  circuit  is  always  interrupted 
at  the  point  of  maximum  current. 

The  interrupter  cam  is  driven  by  the  same  shaft  as  the  rotor. 
One  contact  is  grounded  and  the  other  connected  to  the  ungrounded 
end  of  the  primary.  The  condenser  is  located  on  top  of  the  windings 
and  is  connected  across  the  contact  points.  One  end  of  the  secondary 
is  grounded  through  the  primary  and  the  other  is  connected  to  the 
rotor  of  the  distributor.  Fig.  171  shows  diagrammatically  the  internal 
wiring  of  the  Dixie  Magneto. 

The  Dixie  Magneto  constructed  for  use  on  twin-cylinder  motor- 
cycles has  no  changes  in  its  pole  shoe  or  rotor  construction.  The 


200 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


Fig.  171 — Internal  Wiring  of  Dixie  Magneto 

interrupter  cam  is  arranged  to  break  the  primary  circuit  at  unevenly- 
spaced  intervals  to  compensate  for  the  angle  at  which  the  cylinders 
are  placed.  This  causes  one  spark  to  be  delivered  when  the  rotor  is 
just  leaving  the  trailing  pole  shoe  while  the  other  occurs  after  the 
rotor  has  turned  a  considerable  distance  beyond  the  trailing  pole 
shoe.  This  same  relation  is  always  maintained  whether  in  the 
advanced  or  retarded  position  because  of  the  movable  pole  pieces  in 
the  magneto. 


CHAPTER  XIX 


DUAL  AND  DUPLEX  IGNITION  SYSTEMS 

When  a  magneto  is  used  on  a  heavy  engine  which  cannot  be 
turned  by  hand  at  a  sufficiently  high  speed  to  produce  a  spark  and 
the  engine  does  not  employ  an  electric  starter,  a  battery  ignition 
system  may  be  used  to  obtain  a  spark  at  low  speeds.  This  led  to 
the  adoption  of  two  independent  ignition  systems  employing  a  bat- 
tery ignition  system  for  starting  and  a  magneto  for  continuous 
operation.  With  this  arrangement  two  spark  plugs  were  required 
in  each  cylinder,  one  for  the  battery  ignition  system  and  one  for  the 
mageto  ignition  system.  As  the  battery  plugs  were  not  used  while 
operating  on  the  magneto  they  became  sooted  and  short-circuited 
so  that  they  would  not  operate  when  desired  for  starting. 

To  overcome  this  difficulty  systems  have  been  designed  in  which 
the  magneto  and  battery  ignition  system  use  the  same  set  of  plugs. 
These  are  called  Dual  or  Duplex  systems  of  ignition.  In  some  cases 
a  low  tension  magneto  is  used  with  a  high  tension  coil,  the  primary 
of  which  is  supplied  with  current  either  from  the  magneto  or  battery. 
In  other  types  a  high  tension  magneto  is  used  and  a  separate  induc- 
tion coil  for  the  battery.  The  only  part  used  in  common  is  the  dis- 
tributor of  the  magneto.  A  few  types  called  Dunlex  employ  a  high 
tension  magneto  and  a  low  tension  vibrator  coil  which  is  wired  in 
series  with  the  primary  of  the  magneto. 

REMY 

This  is  a  low  tension  magneto  using  a  high  tension  coil,  the 
primary  of  which  is  supplied  with  current  either  from  the  magneto  or 
from  the  battery. 

Fig.  172  shows  diagrammatically  the  internal  and  external  wiring 
of  the  Remy  Dual  ignition  system.  When  the  dash  coil  is  switched  to 
the  "off"  position  all  circuits  are  open.  When  the  switch  is  turned 
to  the  "M"  (Magneto)  position  the  battery  circuit  is  open  and 
the  current  is  furnished  by  the  magneto.  In  this  position  the  switch 
is  making  connection  between  "A"  and  "B." 

The  primary  circuit  is  as  follows:  The  current  from  the  magneto 
primary  winding,  one  side  of  which  is  grounded,  flows  from  "G"  at 
the  magneto  to  "G"  at  the  coil  which  is  connected  to  the  switch  at 

201 


202 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


Fig.  172 — Internal  Wiring  of  Remy  Dual  System 

"A"  and  then  across  the  switch  plate  to  "B."  From  here  it  flows 
through  the  primary  of  the  coil  to  terminal  "Y"  on  the  coil  which 
is  connected  to  terminal  "Y"  on  the  magneto.  The  interrupter  is 
connected  between  terminal  "Y"  and  ground.  When  the  points 
are  together  the  circuit  is  made  and  when  separated  the  circuit  is 
interrupted,  causing  a  breakdown  of  the  magnetic  field  set  up  by 
the  primary  of  the  coil,  inducing  current  in  the  secondary.  The 
secondary  circuit  is  as  follows:  One  end  is  grounded  at  "R"  on  the 
magneto.  The  other  end  of  the  secondary  winding  of  the  coil  is 
connected  to  the  center  terminal  of  the  distributor  from  which  it  is 
distributed  to  the  terminals  wired  to  the  plugs. 

When  the  switch  is  turned  to  the  "B"  (Battery)  position,  the 
current  is  supplied  to  the  primary  at  the  coil  from  the  battery  instead 
of  the  magneto,  the  switch  now  connecting  "C"  and  "B." 

The  primary  circuit  is  as  follows:  The  current  flows  from  the 
positive  of  the  battery  to  a  terminal  "P"  on  the  coil.  Then  it  flows 
through  a  jumper  in  the  coil  to  terminal  "R"  which  is  connected  by 
cable  to  "R"  on  the  magneto  which  is  the  ground  terminal.  One 
side  of  the  interrupter  being  grounded  and  the  other  side  connected 
to  "Y"  the  current  takes  this  path  when  the  interrupter  points  are 
closed.  It  flows  to  terminal  "Y"  on  the  coil  which  is  connected  to 
the  primary  of  the  coil.  The  other  end  of  the  primary  is  connected 


DUAL  AND  DUPLEX  IGNITION  SYSTEMS 


203 


to  "B."  As  "B"  and  "C"  are  connected  the  current  flows  to  the 
terminal  "N"  and  back  to  the  battery  making  a  complete  circuit. 
When  the  interrupter  points  are  separated  the  circuit  is  broken 
causing  a  collapse  of  the  field  set  up  by  the  primary  of  the  coil  thus 
inducing  the  secondary  current.  The  secondary  circuit  is  the  same 
as  when  operating  on  magneto. 

This  is  the  typical  arrangement  when  a  low  tension  magneto  is 
used  for  dual  ignition  and  all  other  systems  vary  but  little  from  this 
in  any  respect  except  switch  connections. 

BOSCH  DUAL 

In  this  system  a  high  tension  magneto  is  used  and  also  a  high 
tension  coil  with  battery.  They  work  independently  of  each  other 
except  that  they  both  employ  the  same  distributor. 

Fig.  173  shows  diagrammatically  the  internal  wiring  of  the  coil 
and  magneto  of  the  Du-4  Dual  ignition  system  as  well  as  the  external 
connections  from  the  magneto  to  the  coil.  At  A  is  shown  the  in- 


Fig.  173 — Internal  Wiring  of  Bosch  Dual  System 

ternal  wiring  of  the  coil  and  its  connections  to  the  movable  switch 
plate  "X."  At  B  is  shown  how  the  segments  in  the  movable  switch 
plate  connect  the  terminals  of  the  fixed  switch  plate  "Y"  when  in 
different  operating  positions.  At  C  is  shown  the  internal  connec- 


204 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


tions  of  the  magneto  and  how  they  are  wired  to  the  fixed  switch 
plate  "Y"  of  the  coil.  It  is  to  be  noted  that  the  magneto  has  two 
interrupters  as  shown  in  Fig.  174.  One  is  for  the  magneto  and  one 


^, Lock  nut 
^-Contact  block 
.^Segment 
,_  Long  platinum  screw 
:>^  Fastening  screw  for  spring 
•^  Short  platinum,  screw 
>-  Interrupter    lever 
>-  Auxiliary  spring 
^  Spring  post 
^Fastening  screw  for  spring, 
y  Screw  plate 

•^.Spring  for  magneto  interrupter 
nj-Sprinp  for  battery  interrupter^ 
/V.  Interrupter  fastening  screw      < 
-+~  Screw  plate 


Fig.  174 — Dual  Interrupters 

for  the  battery  ignition  system,  each  being  electrically  independent 
of  the  other. 

When  the  coil  is  switched  to  the  "M"  (Magneto)  position  the 
battery  circuit  is  broken  as  the  "5"  terminal  is  not  in  contact  with 
any  segment  on  the  movable  switch  plate.  The  primary  circuit  of 
the  magneto  is  as  follows:  One  end  of  the  primary  winding  is 
grounded.  The  other  end  is  lead  to  the  interrupter  contact  point 
"P"  which  is  in  connection  with  contact  "Q"  which  is  grounded. 

The  secondary  circuit  is  as  follows:  One  end  of  the  secondary 
winding  is  connected  to  the  primary  and  the  other  end  is  connected 
to  the  slip  ring.  Carbon  holder  "3,"  the  brush  of  which  is  in  contact 
with  the  slip  ring,  is  connected  to  terminal  "3"  on  the  switch  plate 
of  the  coil.  A  segment  of  this  movable  switch  plate  connects  term- 
inals "3"  and  "4"  so  that  the  current  is  lead  to  the  distributor  and 
then  to  the  plugs.  The  battery  or  coil  windings  do  not  enter  into 
the  circuits  when  operating  on  magneto. 

If  the  switch  is  turned  to  the  "off"  position  shown  at  B  the 
movable  switch  plate  makes  connection  between  terminals  "2"  and 
"6"  which  short-circuits  the  primary  of  the  magneto  putting  it  out 
of  operation.  The  battery  circuit  is  still  broken  as  the  terminal 
"5"  is  not  connected  to  any  segment  of  the  movable  switch  plate. 
Therefore,  the  battery  system  is  out  of  operation. 

When  the  coil  is  switched  to  the  "B"  (Battery)  position  number 
"2"  terminal  is  still  connected  to  ground  so  that  the  magneto  is  out 
of  operation.  Terminal  "5"  is  now  connected  to  the  segment  shown 
as  a  square  on  the  movable  switch  plate.  The  battery  current 


DUAL  AND  DUPLEX  IGNITION  SYSTEMS  205 

passes  through  the  primary  of  the  coil  and  to  terminal  "1"  of  the 
switch  plate  which  is  connected  to  the  battery  interrupter  on  the 
magneto.  The  secondary  winding  of  the  coil  has  one  end  attached 
to  the  segment  of  the  movable  switch  plate  which  is  in  contact  with 
terminal  "6"  and  is  grounded.  The  other  end  of  the  secondary 
winding  is  connected  to  the  segment  on  the  movable  switch  plate 
which  is  now  in  contact  with  terminal  "4."  This  terminal  is  con- 
nected to  the  distributor  of  the  magneto  from  which  the  current  is 
lead  to  the  spark  plugs. 

The  only  part  used  in  common  for  the  magneto  and  battery 
system  is  the  distributor  so  that  in  reality  two  complete  ignition 
systems  exist  independent  of  each  other  except  that  they  use  the 
same  distributor  and  plugs.  This  condition  is  ideal  and  it  gives  two 
separate  systems  so  that  if  one  goes  dead  the  other  can  easily  be 
used.  This  design  is  typical  of  all  systems  employing  a  high  tension 
magneto  in  a  dual  system  of  ignition. 

VIBRATING  DUPLEX  SYSTEM 

In  order  to  obtain  a  system  which  would  be  simple  and  not  require 
a  separate  high  tension  coil,  a  construction  called  the  vibrating  duplex 
system  has  been  designed  and  used  by  many  ignition  manufacturers. 
It  consists  of  a  switch  and  a  low  tension  vibrator  coil  which  is  wired 
in  series  with  the  primary  of  the  magneto.  In  this  way  the  battery 
supplies  the  necessary  current  to  the  primary  of  the  magneto  and  the 
vibrator  interrupts  it  so  as  to  get  the  induced  secondary  current. 

The  connections  in  this  system  are  made  as  shown  hi  Fig.  175. 
One  side  of  the  battery  is  connected  to  the  coil  and  the  other  side  is 
connected  to  the  terminal  "C"  of  the  switch.  Terminal  "D"  is 
connected  to  ground  and  terminal  "B"  is  connected  to  the  other 
terminal  of  the  coil.  Terminal  "A"  is  connected  to  the  short-cir- 
cuiting terminal  of  the  magneto.  When  the  switch  is  in  the  "off" 
position  it  connects  "A"  to  "D"  which  short-circuits  the  primary 
of  the  magneto.  Terminal  "C"  is  free  so  that  the  battery  circuit 
is  broken. 

When  the  switch  is  turned  to  the  "battery"  position  terminals 
"C"  and  "D"  are  connected  and  likewise  "A"  and  "B."  The 
current  from  the  battery  now  passes  through  the  vibrator  coil  and 
to  terminal  "  S  "  at  the  magneto.  If  the  interrupter  points  are  closed 
the  current  will  be  grounded  through  them  and  the  vibrator  will 
vibrate  but  the  primary  of  the  magneto  does  not  receive  any  of  the 
battery  current.  When  the  interrupter  points  are  separated  the 
current  must  pass  through  the  primary  of  the  magneto  to  get  to 


206 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


ground  and  every  time  that  the  vibrator  interrupts  the  circuit  an 
induced  current  will  be  set  up  in  the  secondary.  In  this  way  a  spark 
or  series  of  sparks  will  be  produced  even  if  the  magneto  is  at  a  stand- 
still or  revolving  slowly. 


Fig.  175 — Internal  Wiring  of  Duplex  System 

When  the  switch  is  turned  to  the  magneto  position  all  the  con- 
tacts at  the  switch  are  open  so  that  the  battery  circuit  is  broken  and 
the  magneto  is  not  grounded.  It  will  thus  operate  as  an  inde- 
pendent high-tension  magneto. 

With  this  system  the  advantage  of  having  battery  ignition  for 
starting  and  magneto  for  operating  has  been  obtained  but  its  entire 
operation  depends  upon  the  magneto  so  that  any  trouble  with  the 
magneto  puts  the  entire  system  out  of  operation. 


CHAPTER  XX 


STARTING  AND  LIGHTING  SYSTEMS 

One  of  the  greatest  improvements  in  the  equipment  of  modern 
motor  vehicles  has  been  the  adoption  of  electric  starting  and  lighting 
systems.  The  unhandy  and  troublesome  lights  formerly  used  have 
been  replaced  by  efficient  electric  lights  ready  to  illuminate  the  road 
at  a  moment's  notice.  The  task  of  cranking  the  engine  by  hand 
which  was  always  laborious,  and  sometimes  dangerous,  has  been 
eliminated  and  the  engine  is  now  spun  easily  whenever  desired  by  an 
electric  cranking  motor. 

Starting  and  lighting  systems  are  generally  divided  into  two 
classes:  first,  single-unit  systems;  second,  two-unit  systems.  In  the 
first  a  single  piece  of  electrical  apparatus,  a  motor-generator,  fur- 
nishes the  current  for  charging  the  storage  battery,  for  ignition,  and 
for  operating  the  lights  and  also  acts  as  a  motor  for  cranking  the 
engine.  The  two-unit  system  has  a  generator  for  furnishing  the 
current  and  a  separate  motor  for  cranking  the  engine. 

In  order  to  understand  the  operation  of  motors  and  generators 
a  brief  explanation  of  the  principles  upon  which  they  operate  will 
first  be  given. 

The  generator  does  not  actually  create  electrical  energy  as  might 
be  implied  from  its  name.  It  simply  generates  or  produces  an  elec- 
tro-motive force  by  means  of  electro-magnetic  induction  which 
causes  current  to  flow.  The  electrical  output  of  a  generator  depends 
upon  the  mechanical  energy  supplied  to  drive  it.  Hence  a  generator 
is  a  piece  of  electrical  apparatus  for  transforming  mechanical  energy 
into  electrical  energy  in  the  form  of  induced  electro-motive  force. 
This  force  causes  electricity  to  flow  through  the  external  circuit  from 
the  positive  terminal  or  point  of  high  potential  to  the  negative 
terminal  or  point  of  low  potential,  just  as  water  flows  from  a  higher 
to  a  lower  level.  In  the  internal  circuit  electricity  flows  from  a  lower 
to  a  higher  potential  due  to  the  induced  electro-motive  force  just 
as  water  is  pumped  from  a  lower  to  a  higher  level. 

Generators  and  motors  are  classified  according  to  their  design  and 
mechanical  construction. 

1 .  Direct  current  machines. 

2.  Alternating  current  machines. 

The  current  in  the  internal  circuit  is  always  alternating  just  as  in 
the  magneto  but  may  be  made  direct  current  in  the  external  circuit 

207 


208 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


by  employing  suitable  moving  contacts  called  a  commutator.  Since 
only  direct  current  machines  can  be  used  for  starting  and  lighting 
systems  because  of  the  storage  battery,  alternating  current  machines 
with  the  exception  of  the  Ford  magneto  will  not  be  discussed  in  this 
chapter. 

The  simplest  form  of  generator  may  be  made  by  revolving  a 
closed  loop  of  wire  in  a  magnetic  field.    Fig.  176  shows  a  loop  of 

wire  mounted  on  a  shaft  which 
may  be  revolved  in  the  magnetic 
field  existing  between  the  north 
and  south  poles  as  shown.  If 
the  loop  is  revolved  as  indicated 
by  the  arrow  the  following  will 
result.  In  the  position  shown 
there  will  be  no  induced  electro- 
motive force  in  the  loop  since  all 
the  lines  of  force  thread  through 
it.  As  it  turns  through  one-quar- 
ter of  a  revolution  the  number 
of  lines  of  force  threading  through 
Fig.  176— Principle  of  Generator  the  loop  are  diminished  at  a 

constantly  increasing  rate  until 

it  reaches  the  dotted  position  where  no  lines  of  force  thread  through 
it.  The  induced  electro-motive  force  depends  upon  the  rate  of 
change  of  the  lines  of  force  threading  through  the  loop  and  will 
therefore  be  greatest  when  the  loop  is  moving  across  the  pole  faces 
with  a  maximum  value  when  the  loop  is  in  the  dotted  position. 
Applying  the  right  hand  rule  (Fig.  110)  the  direction  of  the  current 
flow  is  that  indicated  by  the  arrows  in  Fig.  176.  During  the  second 
quarter  revolution  the  lines  of  force  thread  through  the  opposite 
side  of  the  loop.  The  rate  of  change  and  consequently  the  electro- 
motive force  decreases  until  both  are  zero  again  when  one-half 
revolution  has  been  completed.  During  the  next  half  revolution  the 
same  variations  in  the  induced  electro-motive  force  occur  but  in  the 
opposite  direction.  The  current  is  reversed  twice  each  revolution, 
an  alternating  current  flowing  around  the  loop. 

To  utilize  the  current  flowing  in  a  closed  loop  when  it  is  rotated 
in  a  magnetic  field  some  mechanical  device  must  be  used  to  lead  the 
current  from  the  rotating  loop  so  it  will  flow  through  an  external 
circuit.  This  is  accomplished  by  attaching  the  ends  of  the  loop  to 
metal  contacts  against  which  are  held  stationary  pieces  called 
brushes.  If  each  brush  is  connected  first  with  one  end  and  then 
with  the  other  end  of  the  revolving  loop  and  the  change  is  made  at  the 


STARTING  AND  LIGHTING  SYSTEMS 


209 


Fig,  177— Simple 
Commutator 


instant  the  current  in  each  side  of  the  loop  is  reversing  the  current 
in  the  outside  circuit  will  always  flow  in  the  same  direction.    This 
is  accomplished  by  means  of  a  commutator 
(Fig.  177). 

The  simplest  form  of  commutator  consists 
of  a  split  ring  the  segments  "S-l"  and  "S-2" 
being  insulated  from  each  other  and  also  from 
the  shaft.  The  brushes  "  B-l "  and  "  B-2  "  rest 
on  the  commutator  at  diametrically  opposite 
points  collecting  the  current  and  delivering  it 
to  the  lamps  "L." 

Assuming  that  the  current  in  "C-l "  is  flow- 
ing to  the  brush  "B-l"  the  current  in  "C-2" 
must  be  flowing  in  the  opposite  direction  or  away  from  brush 
"B-2."  Hence  "B-l"  is  positive  and  "B-2"  negative.  The  brush 
"B-l"  bears  on  the  segment  "S-l"  as  long  as  the  current  in 
"C-l"  continues  to  flow  in  this  direction.  At  the  instant  the  cur- 
rent in  "C-l"  starts  to  flow  in  the  opposite  direction  the  segment 
"S-l"  leaves  this  brush  and  "S-2"  just  makes  contact  with  "B-l." 
The  current  in  "C-2"  has  also  reversed  and  now  flows  to  segment 
"S-2."  Hence  "S-2"  now  delivers  current  to  brush  "B-l"  which 
still  continues  to  be  the  positive  brush.  In  the  same  way  brush 
"B-2"  is  always  the  negative  brush  and  the  current  delivered  to 
the  lamps  always  flows  in  the  same  direction. 

When  but  a  single  loop  of  wire  is  used  the  induced  electro-motive 
force  will  necessarily  be  low.  By  increasing  the  number  of  turns, 
the  induced  electro-motive  force  is  increased  proportionately.  With 
a  single  loop,  the  current  delivered  will  not  be  steady  although  always 
in  the  same  direction.  The  variations  in  the  current  flow  are  due  to 
the  change  in  the  induced  electro-motive  force  from  a  maximum  to 
zero  as  the  loop  is  revolved.  If  another  loop  is  placed  at  right 
angles  to  that  shown  in  Fig.  176  the  current  flow  in  this  loop  will  be 
a  maximum  when  it  is  zero  in  the  other  loop.  As  the  two  loops  are 
revolved  the  current  flow  in  one  increases  as  that  in  the  other  de- 
creases giving  a  less  pulsating  current  in  the  external  circuit.  Fig. 
178  shows  graphically  the  difference  between  the  current  delivered 
by  a  single  loop  and  that  delivered  by  two  loops  at  right  angles  to 


i*      \4     Vr      \4    rf/ 

|f lH«wolMtion  J 


Fig.  178 — Graphic  Representation  of  Current  in  External  Circuit 


210  MOTOR  VEHICLES  AND  THEIR  ENGINES 

each  other.    By  equally  spacing  a  great  number  of  coils  a  continuous 
current  output  and  high  electro-motive  force  is  obtained. 

To  concentrate  the  magnetic  field  between  the  poles  of  the  field 
magnets  and  also  to  support  the  coils  of  wire  a  laminated  armature 
of  soft  iron  is  used. 


Fig.  179 — Drum  Type  Armature 

The  armature  may  be  ring-shaped  with  the  coils  wound  around 
it  or  it  may  be  of  the  slotted-drum  type  (Fig.  179).  The  latter  is  the 
type  of  armature  universally  used  on  starting  motors  and  lighting 
generators.  Although  the  armature  coils  are  all  connected  in  series 
with  each  other  there  must  be  a  commutator  segment  for  every  coil 
of  wire  wound  on  the  armature.  This  is  necessary  so  that  the  cur- 
rent flowing  in  any  particular  coil  has  a  path  through  the  brushes 
to  the  outside  circuit  at  the  instant  the  current  flowing  in  it  is  a 
maximum. 

Commutators  are  built  up  of  copper  segments  insulated  from 
each  other  by  mica  inserts  the  segments  projecting  slightly  above  the 
mica.  The  commutator  is  finished  by  being  turned  true  so  that  the 
carbon  brushes  always  make  good  contact  with  its  surface. 

In  order  to  set  up  a  strong  magnetic  field  between  the  pole  pieces, 
the  field  magnets  of  motors  and  generators  are  electro-magnets. 
Part  or  all  of  the  current  generated  in  the  armature  is  sent  through 
coils  of  wire  wound  on  the  field  pieces.  Of  course  no  current  would 
be  generated  in  the  armature  at  starting  if  there  was  not  some  mag- 
netic field  existing  between  the  pole  pieces.  The  soft  iron  field 
pieces  retain  sufficient  "residual"  magnetism  to  set  up  a  weak  field 
which  in  turn  generates  a  weak  current.  This  current  flows  through 
the  field  windings  increasing  the  magnetic  field  which  in  turn  in- 
creases the  generated  current.  In  this  way  the  machine  "  builds 
up"  until  it  has  reached  its  normal  operating  condition. 

Field  windings  may  be  arranged  in  any  of  the  following  ways* 
series  shunt,  or  compound. 


STARTING  AND  LIGHTING  SYSTEMS 


211 


Fig.  180  shows  a  simple  two-pole  machine  in  which  all  the  current 
generated  in  the  armature  passes  through  the  field  coils.  Hence, 
heavy  wire  is  used  to  carry  the  current  and  but  a  small  number  of 
turns  are  necessary  to  give  the  desired  strength  of  magnetic  field. 
This  is  known  as  a  series  wound  machine.  Generators  of  this  de- 


Fig.  180 — Series  Generator 

scription  are  not  used  for  lighting  motor  vehicles.  This  is  because 
the  voltage  varies  greatly  when  the  resistance  of  the  external  circuit 
is  changed  hence  they  are  only  suitable  for  supplying  practically 
constant  current.  Series  wound  motors,  however,  are  always  used 
because  of  the  great  starting  torque  obtained.  This  will  be  discussed 
more  fully  later  in  this  chapter. 

Fig.  181  shows  the  field  windings  so  arranged  that  only  part  of 
the  current  generated  in  the  armature  flows  through  them.     Hence, 


Fig.  181 — Shunt  Generator 

fine  wire  is  used  and  a  great  many  turns  are  necessary  to  produce 
the  desired  strength  of  magnetic  field.  This  is  known  as  a  shunt 
wound  machine.  A  shunt  generator  "builds  up"  in  the  same  way  a 
series  generator  does.  The  voltage  of  a  shunt  wound  generator  falls 
off  as  the  load  on  it  is  increased  but  when  used  as  a  lighting  generator 
the  storage  battery  carries  any  extra  load  keeping  the  voltage  con- 
stant on  the  line.  Shunt  wound  starting  motors  are  not  used  because 
of  their  low  starting  torque. 


212 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


Fig.  182  shows  a  two-pole  compound  wound  machine.  The  field 
windings  are  made  up  of  both  shunt  and  series  coils.  When  the  field 
windings  are  arranged  so  that  they  oppose  or  "buck"  each  other 


Fig.  182 — Compound  Generator 

the  machine  is  said  to  be  "differentially  wound."  When  the  field 
windings  are  so  arranged  that  they  aid  each  other  the  machine  is 
said  to  be  "cumulative." 

The  operation  of  the  motor  depends  upon  the  resultant  field  set 
up  when  a  conductor  through  which  current  is  flowing  is  placed  in  a 
strong  magnetic  field. 


A  B 

Fig.  183 — Field  About  a  Current  Carrying  Conductor 

Fig.  183A  shows  the  field  existing  about  a  wire  when  current  is 
flowing  through  it  and  Fig.  183B,  the  field  resulting  when  it  is  placed 
in  a  uniform  field  flowing  from  left  to  right.  The  lines  of  force  above 
the  wire  flowing  to  the  right  join  those  of  the  field  flowing  to  the  right 
and  thus  strengthen  the  field  above  the  wire.  Those  below  the  wire 
flowing  to  the  left  neutralize  some  of  the  lines  of  force  flowing  to  the 
right  and  weaken  the  field  below  the  wire.  Thus  a  strong  field  is 


STARTING  AND  LIGHTING  SYSTEMS  213 

built  up  above  the  wire  and  a  weak  field  below  it  resulting  in  a  force 
which  causes  the  wire  to  move  down  due  to  the  elastic  action  of  the 
lines  of  force. 

Fig.  184  shows  the  effect  of  sending  current  through  a  loop  of 
wire  free  to  revolve  between  opposite  poles  of  a  magnet.  When 
current  flows  in  at  "A"  and  out  at  "B"  the  field  is  weakened  below 
"A"  and  above  "B."  This  causes  the  loop  to  revolve  in  a  counter 
clock-wise  direction.  When  the  number  of  loops  and  the  strength  of 
current  passing  through  them  is  increased  the  turning  force  will  be 


Fig.  184 — Principle  of  Motor 

greatly  increased.  When  the  field  between  the  poles  is  strengthened 
by  placing  the  coils  on  an  armature  and  spacing  them  equally  an 
even  torque  is  obtained.  This  is  identical  with  the  construction 
used  on  generators.  Sending  current  through  the  armature  of  a 
generator  causes  it  to  revolve  and  the  machine  becomes  a  motor.  A 
motor,  therefore,  is  a  machine  for  transforming  electrical  energy  into 
mechanical  energy. 

To  determine  the  direction  of  rotation  the  left  hand  should  be 
held  as  shown  in  Fig.  110  the  middle  finger  indicating  the  direction 
the  current  is  flowing  through  the  coil  and  the  forefinger  the  direction 
of  magnetic  flux.  The  thumb  will  then  indicate  the  direction  of 
rotation.  When  run  as  a  motor  current  is  always  sent  through  the 
armature  of  a  machine  in  the  opposite  direction  to  its  flow  when 
operating  as  a  generator.  The  direction  of  rotation  of  the  machine 
will  be  the  same  when  running  as  a  motor  as  when  driven  as  a  gener- 
ator. This  can  be  proved  by  applying  the  left  hand  or  motor  rule. 

Motors  and  generators  used  for  starting  and  lighting  purposes 
are  almost  always  four-pole  machines.  The  field  magnets  are  made 
as  compact  as  possible  so  as  to  concentrate  the  magnetic  field.  The 
magnets  are  supported  by  an  iron  case  which  completes  the  magnetic 
circuit  and  encloses  all  windings,  brushes,  and  armature  protecting 
them  from  dampness  and  dirt. 

Due  to  the  great  variation  in  the  speed  at  which  the  engine  of  a 
motor  vehicle  runs  the  voltage  of  a  generator  will  necessarily  vary. 


214 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


Most  generators  are  designed  to  start  charging  the  storage  battery 
at  a  car  speed  of  8  or  10  miles  per  hour.  As  the  speed  is  increased 
the  voltage  unless  regulated  in  some  manner  will  become  excessive, 
resulting  in  burned-out  lights,  excessive  sparking  at  the  commutator, 
and  too  high  a  charging  rate.  Therefore,  some  form  of  regulation 
must  be  employed  to  keep  the  voltage  or  current  supplied  constant 
at  the  higher  speeds. 

Several  methods  of  accomplishing  regulation  are  employed  and 
those  used  on  the  systems  discussed  in  this  chapter  are  explained  as 
each  system  is  described. 


Fig.  185 — Lighting  System  Without  Cutout 

Fig.  185  shows  a  wiring  diagram  of  a  compound  wound  generator 
"G"  connected  to  charge  a  storage  battery  "B"  and  furnish  current 
for  lights  "L."  As  long  as  the  speed  of  the  engine  driving  the  gener- 
ator is  high  enough  the  voltage  at  the  generator  will  be  greater  than 
that  of  the  battery  causing  current  to  flow  as  indicated  by  the  heavy 
arrows.  However,  if  the  engine  speed  is  reduced  the  voltage  at  the 
generator  will  fall  off  and  the  voltage  of  the  battery  will  exceed  that 
at  the  generator.  This  will  cause  current  to  flow  in  the  direction 
indicated  by  the  dotted  arrows.  The  battery  discharges  through  the 
generator  causing  it  to  run  as  a  motor.  To  prevent  the  battery 
from  discharging  when  the  engine  is  slowed  down  or  stopped  an  auto- 
matic cut-out  is  placed  in  the  circuit. 

Fig.  186  shows  a  simple  single-unit  starting  and  lighting  system 
with  a  cut-out.  The  current  from  the  generator  flows  through  the 
potential  coil  "P"  having  a  great  many  turns  of  fine  wire,  causing 
the  soft  iron  core  "G"  to  become  magnetized.  When  the  voltage 
at  the  generator  becomes  sufficient,  enough  current  will  be  forced 
through  the  high  resistance  potential  coil  "P"  to  make  the  core  "G" 


STARTING  AND  LIGHTING  SYSTEMS 


215 


Fig.  186 — Starting  and  Lighting  System  With  Cutout 

so  strongly  magnetic  that  the  soft  iron  disc  "  D  "  is  drawn  to  it  against 
the  action  of  the  spring  "R."  This  causes  the  contact  points  "C" 
to  close,  the  current  flowing  through  the  low  resistance  series  coil 
"S"  to  the  battery  "B"  and  lights  "L."  Only  a  little  current  con- 
tinues to  flow  through  "P"  when  the  cut-out  closes  but  the  series 
coil  "S"  keeps  the  core  "G"  sufficiently  magnetized  to  hold  the  cut- 
out  closed.  If  the  voltage  at  the  generator  falls  off  until  it  is  less 
than  that  of  the  battery,  current  from  the  battery  will  start  to  flow 
in  the  opposite  direction  through  the  coil  "S."  Coil  "P"  tends  to 
keep  the  core  "G"  magnetized,  though  the  current  flowing  through 
it  has  decreased,  but  coil  "S"  now  tends  to  magnetize  the  core  "G" 
in  the  opposite  direction.  This  results  in  a  weakening  of  the  magnetic 
strength  of  "G"  so  that  it  cannot  hold  "D"  against  the  pull  of  the 
spring  "R."  The  cut-out  opens  separating  the  contact  points  "C" 
and  prevents  the  battery  current  from  flowing  back  through  the 
generator.  The  lights  are  now  supplied  by  the  battery  until  the 
voltage  at  the  generator  becomes  great  enough  to  close  the  cut-out. 
When  the  engine  stops  current  is  drawn  from  the  battery  by  closing 
the  switch  "A."  The  current  flows  through  the  generator  in  the 
opposite  direction  causing  it  to  turn  as  a  motor  and  crank  the  engine. 

NORTH  EAST 

The  North  East  system  consists  of  a  single  unit  motor-generator 
which  furnishes  current  for  charging  the  storage  battery,  lights, 
ignition,  and  cranks  the  engine  when  starting.  The  machine  is  four- 


216 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


3SS.4-G-1  ST»»TE« 


JFTAffTlM* 


pole  compound  wound  and  is  driven  by  a  silent  chain  from  the  crank 
shaft  at  three  times  engine  speed. 

Fig.  187  shows  the  internal  wiring  of  the  North  East  motor- 
generator  installation  on  the  Dodge  car.  The  shunt  and  series  field 
windings  are  clearly  shown  and  also  the  windings  on  the  cut-out.  A 
fuse  is  provided  which  protects  the  shunt  field  windings. 

It  will  be  noticed  that  one  end  of  the  shunt  field  winding  is  at- 
tached to  a  third  brush.  This  brush  is  the  voltage  regulating  device 

used  on  this  system.  As  the 
speed  at  which  the  generator 
is  driven  increases  the  voltage 
in  the  armature  coils  between 
the  third  brush  and  negative 
brush  falls  causing  less  current 
to  be  forced  through  the  shunt 
field.  This  correspondingly 
reduces  the  strength  of  the 
magnetic  field  and  compen- 
sates for  the  increased  speed 
at  which  the  machine  is  being 
driven.  Charging  starts  at  a 
car  speed  of  about  10  miles 
per  hour,  the  maximum  charg- 
ing rate  of  6  amperes  being 
reached  at  a  speed  of  about 
17  miles  per  hour.  At  ex- 
tremely high  speeds  the  charg- 
ing rate  falls  off  becoming  as 
low  as  3  amperes. 

To  increase  the  charging  rate  the  third  brush  is  moved  in  the 
direction  the  armature  rotates.  This  setting  should  never  be  changed 
unless  the  battery  charge  is  habitually  low  or  the  charging  rate  too 
high.  Too  high  a  charging  rate  is  indicated  by  the  battery  requiring 
a  too  frequent  addition  of  water. 

Fig.  188  shows  the  complete  wiring  of  the  North  East  single  unit 
system  of  starting  and  lighting  on  the  Dodge  car.  When  running 
10  miles  per  hour  or  faster  the  cut-out  is  closed  and  the  generator 
furnishes  current  for  charging  the  battery,  the  head  lights,  tail  lights, 
dash  light,  ignition  system,  and  the  electric  horn  when  the  push 
button  is  pressed. 

The  ammeter  on  the  dash  reads  "  charge  "  when  current  is  passing 
into  the  battery.  When  the  speed  is  reduced  sufficiently  the  cut-out 
opens  and  the  battery  furnishes  the  current  the  ammeter  reading 


Fig.  187 — Internal  Wiring  of 
North  East 


\ 


217 


218 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


"discharge."  To  start  the  engine  the  starting  switch  is  closed  which 
draws  current  from  the  battery  causing  the  motor-generator  to  revolve 
as  a  motor  and  crank  the  engine.  This  heavy  current  does  not  pass 
through  the  ammeter  so  the  windings  will  not  be  burned  out. 

LEESE-NEVILLE 

The  Leese-Neville  starting  and  lighting  system  consists  of  two 
units,  a  shunt  wound  four-pole  generator  and  a  series  wound  motor. 
The  generator  furnishes  current  for  charging  the  storage  battery, 
lights,  and  ignition  and  the  motor  cranks  the  engine  drawing  current 
from  the  storage  battery. 

The  generator,  running  at  approximately  engine  speed,  is  driven 
by  a  chain  from  the  crank  shaft.  Third  brush  regulation  is 
used  which  has  already  been  explained.  An  automatic  cut-out  is 
provided  to  prevent  the  battery  from  discharging  through  the  genera- 
tor at  low  engine  speeds  and  is  of  the  usual  construction. 


CIRCUIT   BREAKER 


FUSE 


GENERATOR 


B.-4 


Fig.  189 — Internal  Wiring  of  Leese-Neville 

Fig.  189  shows  the  internal  wiring  of  the  generator  and  circuit 
breaker  or  cut-out.  In  the  grounded  system  the  brush  connected 
to  "A-2"  is  internally  grounded  and  only  one  cable  comes  from  the 
cut-out.  The  charging  rate  is  controlled  by  the  position  of  the  third 
brush.  The  shunt  field  is  protected  by  a  10-ampere  fuse. 

The  motor  is  attached  to  the  crank  case  and  drives  the  flywheel 
of  the  engine  through  the  gear  teeth  cut  in  its  circumference  by 
means  of  a  small  pinion  directly  driven  by  the  motor  armature  shaft. 


STARTING  AND  LIGHTING  SYSTEMS 


219 


The  armature  shaft  carries  a  worm  gear  (Fig.  190).  The  pinion 
"P"  has  a  female  thread  which  fits  on  the  worm  and  when  the  arma- 
ture shaft  revolves  the  pinion  tends  to  stand  still  and  is  screwed  out 


Fig.  190— Bendix  Drive 

engaging  with  the  teeth  on  the  flywheel.  When  the  engine  starts 
it  turns  the  pinion  at  a  greater  rate  of  speed  than  the  armature  shaft 
is  turning  causing  the  pinion  to  be  screwed  back  to  its  former  position 
disengaging  the  flywheel  gear.  This  method  is  called  the  Bendix 
drive. 


Fig.  191— Wiring  on  White 

Fig.  191  shows  the  complete  wiring  of  the  starting  and  lighting 
system  installed  on  the  Staff  Observation  Car.  The  motor  is  sup- 
plied with  current  from  the  storage  battery  when  the  starting  switch, 
which  is  located  on  the  floor  boards  of  the  car,  is  closed.  The  gen- 
erator charges  the  battery  and  supplies  the  lights  with  current  when 
the  cut-out  is  closed  and  the  battery  supplies  the  lights  when  the 


220 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


cut-out  opens.  A  circuit-breaker  is  provided  in  the  lighting  cir- 
cuit which  takes  the  place  of  fuses  opening  when  there  is  a  ground 
on  the  line. 

BIJUR 

The  Bijur  Lighting  System  as  installed  on  the  Nash  Trucks  con- 
sists of  a  shunt  wound  generator  driven  by  a  silent  chain  from  the 
pump  shaft. 

Fig.  192  is  an  internal  wiring  diagram  showing  all  circuits  except 
the  connections  to  the  lights.  A  cut-out  is  provided  which  operates 


Fig.  192— Internal  Wiring  of  Bijur 

in  the  usual  manner  the  storage  battery  furnishing  current  when  the 
cut-out  is  open. 

The  voltage  regulator  is  of  the  vibrating  variable  resistance  type. 
The  voltage  regulating  unit  as  shown  in  Fig.  192  at  "B"  consists  of 
a  core  having  a  single  winding  connected  in  parallel  with  the  arma- 
ture. The  current  in  the  winding  and  the  resulting  magnetic  pull 
of  the  core  will  depend  upon  the  pressure  developed  by  the  generator. 
Opposite  one  end  of  the  core  is  a  vibrating  armature  which  is  spring 
retracted  from  the  core.  When  the  armature  is  retracted  it  makes 
contact  so  that  there  is  a  by-pass  around  the  resistance  "D"  which 
is  in  series  with  the  field  winding  of  the  generator.  With  the  vibra- 
ting armature  in  this  position  the  shunt  field  winding  receives  the 
full  pressure  developed  by  the  generator.  With  increasing  generator 
speed  the  voltage  increases  until  the  armature  develops  7.75  volts, 
and  at  this  electrical  pressure  the  regulator  begins  to  function  and 


STARTING  AND  LIGHTING  SYSTEMS  221 


will  maintain  this  voltage  across  the  generator  brushes  at  all  higher 
speeds. 

With  increasing  generator  speed  the  voltage  will  tend  to  rise 
above  7.75.  However,  if  this  value  is  exceeded  by  a  very  small 
amount,  the  increased  pull  on  the  armature  of  the  regulating  unit 
will  overcome  the  spring  pull  and  the  armature  will  be  drawn  towards 
the  core,  thus  opening  the  contacts  and  inserting  the  resistance  "D" 
in  the  generator  field  circuit.  The  added  resistance  in  the  field 
circuit  decreases  the  exciting  current  in  the  field  winding  and  the 
voltage  developed  by  the  armature  tends  to  drop  below  the  normal 
value.  If  the  voltage  drops  slightly  below  the  normal  the  pull  of 
the  spring  on  the  regulator  armature  predominates  and  this  armature 
moves  away  from  the  core  and  closes  the  cut-out  which  short-circuits 
the  resistance  and  permits  the  exciting  field  current  to  increase. 
This  cycle  of  operations  is  repeated  at  rapid  intervals  and  maintains 
the  generator  voltage  constant  at  all  speeds  above  the  critical  value 
at  which  it  develops  7.75  volts  with  the  resistance  cut  out  of  the 
field  circuit. 

The  rapidity  of  vibration  depends  to  a  large  extent  upon  speed, 
but  in  general  the  regulator  armature  vibrates  at  the  rate  of  one 
hundred  to  one  hundred  and  fifty  times  per  second.  The  actual 
voltage  developed  by  the  generator  is  made  up  of  a  series  of  very 
small  impulses  the  mean  value  of  which  is  7.75  volts.  This  is  the 
constant  value  for  which  the  regulator  is  adjusted. 

It  is  obvious  that  increasing  the  tension  of  the  regulator  spring 
will  increase  the  constant  voltage  which  the  generator  will  maintain. 
Under  no  circumstances  should  the  regulator  spring  tension  be 
increased  in  an  attempt  to  have  the  generator  charge  at  a  higher  rate 
at  low  speed.  The  generator  cannot  begin  to  charge  until  the  cut- 
out has  closed  and  the  closing  of  the  cut-out  is  independent  of  the 
action  of  the  regulator.  This  cut-out  closes  after  the  generator 
reaches  a  speed  at  which  it  develops  6.5  volts,  and  no  adjustment 
of  the  regulator  or  cut-out  can  change  the  charging  rate  at  low  speed. 
Increasing  the  tension  of  the  regulator  spring  so  that  the  generator 
will  develop  a  constant  voltage  in  excess  of  7.75  volts  will  result  in 
excessive  current  to  the  battery  overcharging  it  or  causing  the 
generator  to  overheat  with  the  possibility  of  burning  it  out. 

In  addition  to  the  resistance  in  series  with  the  shunt  field  winding 
there  is  another  resistance  "E"  which  is  connected  in  parallel  with 
the  field  winding.  The  function  of  this  resistance  is  to  absorb  the 
field  energy  when  the  regulator  contacts  are  opened  and  reduce 
sparking  at  the  contacts. 


222 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


Fig.  193 — External  Wiring  on  Nash 

Fig.  193  shows  the  complete  wiring  of  the  lighting  system  on  the 
Nash  Trucks. 

DELCO 

The  Delco  Starting  and  Lighting  System  as  used  on  the  Cadillac 
Car  consists  of  a  single  unit  motor-generator  which  furnishes  the 
current  for  charging  the  storage  battery,  the  lights,  and  ignition 
system  and  also  runs  as  a  motor  cranking  the  engine.  The  motor- 
generator  is  a  four-pole  machine  with  separate  sets  of  field  and  arma- 
ture windings  necessitating  two  commutators  being  used  which  are 
located  at  opposite  ends  of  the  armature.  The  motor  is  series 
wound  and  the  generator  shunt  wound.  The  motor-generator,  when 
acting  as  a  generator,  is  driven  at  engine  speeds  by  the  fan  shaft 
which  in  turn  is  driven  by  a  silent  chain  from  the  cam  shaft  at  the 
front  end  of  the  engine.  To  prevent  the  voltage  of  the  current 
generated  from  rising  too  high  when  the  engine  is  running  at  high 
speeds  the  third  brush  system  of  current  regulation  is  employed 
which  has  been  explained. 

When  acting  as  a  motor  the  sole  function  of  the  motor-generator 
is  to  crank  the  engine.  In  starting  first  the  operator  pushes  down  the 
ignition  lever  on  the  combination  switch.  This  closes  the  ignition 
circuit  and  the  circuit  between  the  storage  battery  and  the  generator 
windings  on  the  motor-generator  causing  the  armature  to  revolve 
slowly. 


*  STARTING  AND  LIGHTING  SYSTEMS 


223 


A  ratchet  clutch  (Fig.  194)  in  the  front  end  of  the  generator  allows 
the  armature  to  rotate  ahead  of  the  driving  shaft.  The  clicking 
noise  that  is  heard  when  the  ignition  switch  is  turned  on  comes  from 
this  clutch. 


GENERATOR  COMMUTATOR  tfND£R  THIS  COVER 

x "—MOTOR  COMMUTATOR  UNDER  THIS  COVEH 

*s^  ^~~~  STA  RTE  R   BUTTON 

PlMtON  CM  ARK4TURE   SHAFT 

[^  JDLER  GEARS  CONTAIN IN'G 

Ml  -•         •     'Hpfc       ^^x^^    .  OVER-RWNIN6   CLUTCH  '^   HU3 

^*  ^         GEAR  TEETH.  CUT  ON  FLYWHEEL 


GENEPATOR 
DRIVING 

AT  THIS  END 


WIRE  TO  MOTOR  GENERATOR 


Fig.  194 — Installation  of  Delco  on  Cadillac 

As  the  starter  button  is  pushed  down  it  first  causes  the  starter 
gears  to  mesh  with  the  teeth  on  the  flywheel.  The  proper  meshing 
of  the  gears  is  made  easy  by  the  slow  rotation  of  the  armature  which 
begins  as  soon  as  the  ignition  is  turned  on.  As  the  starter  button  is 
pushed  further  down  the  circuit  between  the  storage  battery  and  the 
generator  windings  of  the  motor-generator  is  broken  at  "X"  (Fig.  195). 
As  the  movement  of  the  starter  button  is  completed  the  circuit  is 
closed  between  the  storage  battery  and  the  motor  windings  on  the 
motor-generator  by  the  motor  brushes  coming  in  contact  with  the 
commutator,  causing  it  to  act  as  a  powerful  electric  motor,  which 
rapidly  cranks  the  engine. 

The  gear  ratio  between  the  armature  shaft  and  the  crank  shaft 
being  approximately  25  to  1,  the  armature  would  be  driven  at  an 
excessively  high  rate  of  speed  after  starting  the  engine  before  the 
operator  let  the  starter  button  back,  if  it  were  not  for  an  over-running 
clutch^in^hejiub  of  the  idler  gears  between  the  flywheel  and  the 


224 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


armature  shaft.  The  electric  motor  cranks  the  engine  through  this 
clutch  but  after  the  engine  has  started  and  begins  to  run  faster  than 
the  electric  motor  the  clutch  releases. 

The  starter  button  is  let  up  as  soon  as  the  engine  is  running  under 
its  own  power.  The  first  movement  of  the  button  breaks  the  circuit 
between  the  electric  motor  and  the  storage  battery  by  lifting  the 
brushes  from  the  commutator.  A  further  movement  causes  the 
starter  gears  to  slide  out  of  mesh  and  the  release  of  the  button  com- 
pletes the  circuit  between  the  generator  and  the  storage  battery  at 
"X"  which  was  broken  when  the  starter  button  was  pushed  down. 
The  engine  running  and  the  circuit  being  closed  between  the  storage 
battery  and  the  generator  windings  of  the  motor-generator  the 
generation  of  current  begins. 


MLAO  ll«HT«  P^  4f 

D— i 

»M          »CA* 


Fig.  195 — Internal  Wiring  of  Delco 

Fig.  195  is  a  complete  wiring  diagram  of  the  starting,  lighting,  and 
ignition  system  used  on  the  Cadillac  Car.  Circuit  breakers  take  the 
place  of  fuses  in  the  lighting  circuit  and  no  cut-out  is  provided.  When 
the  generator  voltage  is  less  than  the  voltage  of  the  battery,  current 
will  flow  back  through  the  generator.  The  amount  flowing  is  some- 
what less  than  that  flowing  through  it  when  first  starting.  This  is 
so  little  that  it  is  practically  negligable  (about  5  amperes).  The  cir- 
cuit between  the  generator  and  battery  is  broken  when  the  ignition 
switch  is  thrown  off. 

A  Delco  generator  with  a  single  set  of  windings  is  installed  on 
some  Standardized  B  Trucks.  It  furnishes  current  for  lights  and 
ignition  but  does  not  crank  the  engine.  No  cut-out  is  provided 


STARTING  AND  LIGHTING  SYSTEMS 


225 


except  the  ignition  switch  which  breaks  the  circuit  between  generator 
and  battery  when  in  the  "off"  position.  When  thrown  to  the  "on" 
position  the  generator  will  turn  slowly  as  a  motor  until  the  engine  is 
started  causing  a  "clicking"  noise  due  to  the  over-running  clutch 
which  permits  it  to  turn  free  of  the  engine.  As  in  the  system  on  the 
Cadillac  Car  very  .little  current  is  used  in  this  way. 

FORD  MAGNETO 

This  magneto  may  be  classified  as  a  high  frequency  alternating 
current  magneto.     It  serves  merely  as  a  source  of  primary  current 


Magneto  Coil  Spool 

Copper  Wire 

End  of  Ribbon   1 
Grounded  Here  J 

To  Coil 

Magneto  Coil  Support 


Magnet 
Flywheel 

Magnet  Clamp 


Fig.  196 — Ford  Magneto 


for  the  vibrating  coil  type  of  ignition  system  and  for  supplying 
current  for  lights. 

The  construction  is  as  shown  in  Fig.  196.  The  sixteen  armature 
coils  are  stationary  and  are  wound  around  cores  of  soft  iron  which 
are  supported  on  an  iron  frame.  An  equal  number  of  permanent 
magnets  of  the  horseshoe  type  are  secured  to  a  non-magnetic  ring 
attached  to  the  flywheel  and  revolve  with  it. 


226  MOTOR  VEHICLES  AND  THEIR  ENGINES 

The  north  poles  of  two  adjacent  magnets  are  joined  together  and 
likewise  the  next  pair  of  south  poles.  When  a  pair  of  north  poles 
are  in  front  of  the  core  of  one  coil,  the  magnetic  flux  will  flow  in 
through  this  core  across  the  supporting  frame  and  out  through  the 
cores  of  the  adjacent  coils  to  the  south  poles  of  the  magnets.  When 
the  flywheel  makes  J^  of  a  revolution  the  coil  cores  which  were 
opposite  the  north  poles  of  the  magnets  will  be  opposite  the  south 
poles  causing  a  complete  reversal  of  magnetic  flux  to  take  place  in 
every  coil  core.  This  induces  a  voltage  causing  current  to  flow  in 
each  of  the  coils.  The  coils  are  connected  in  series  and  one  end  is 
grounded.  The  other  end  is  connected  to  the  insulated  binding  post 
on  the  outside  of  the  flywheel  housing  from  which  the  current  supply 
is  drawn.  Hence,  as  the  flywheel  revolves  an  alternating  current  of 
high  frequency  will  be  obtained  from  this  magneto.  This  current  is 
used  for  exciting  the  primary  of  the  ignition  system  as  well  as  for 
lighting  purposes. 

As  there  is  no  regulation  in  the  system  to  control  the  voltage  or 
output,  the  current  generated  will  depend  directly  upon  the  speed  of 
the  engine.  Therefore,  the  faster  the  engine  goes  the  better  will  be 
the  results  obtained  from  the  ignition  system  and  likewise  the  inten- 
sity of  the  lights  will  increase.  It  will  often  be  noticed  on  Ford  Cars 
that  there  is  a  considerable  variation  in  the  intensity  of  the  lights. 
Since  the  current  generated  is  alternating  a  storage  battery  cannot 
be  connected  in  the  line  to  overcome  these  difficulties. 


CHAPTER  XXI 


POWER  TRANSMISSION 

To  transmit  the  power  developed  by  the  engine  to  the  wheels  of 
a  motor-propelled  vehicle  certain  parts  are  necessary  because  of  the 
conditions  under  which  a  motor  vehicle  is  operated.  The  application 
of  the  engine  power  to  the  driving  wheels  through  these  parts  is  called 
Power  Transmission  and  their  arrangement  will  be  discussed  in  this 
chapter. 

The  units  composing  the  power-transmission  system  are  prac- 
tically the  same  on  all  modern  trucks  and  motor  cars  but  their  ar- 
rangement varies,  depending  upon  the  method  of  drive  and  the  type 
of  units  used.  The  following  units  will  be  found  on  all  modern 
machines;  a  clutch,  a  transmission  or  gear  set,  drive  shafts,  universal 
joints,  differentials,  and  axles  extending  to  the  driven  members 
(chain  sprockets  or  wheels). 

When  the  power  is  transmitted  to  the  rear  wheels  only,  the  ar- 
rangement of  the  parts  will  be  as  shown  in  Fig.  197.  This  arrangement 
is  typical  of  light  cars  of  two  wheel  drive,  except  the  Ford  in  which 
the  parts  are  arranged  as  shown  in  Fig.  199.  In  Fig.  197  the  power 
is  transmitted  from  the  engine  through  the  clutch  "  A"  to  the  trans- 
mission "B"  then  through  the  drive  shaft  "C"  with  universal  joints 
"D"  to  the  differential.  The  differential  transmits  the  power  to 
the  rear  wheels. 

If  the  engine,  clutch,  and  transmission  are  not  a  unit  power 
plant,  that  is,  if  they  are  not  contained  in  the  same  housing  it  will  be 
necessary  to  have  an  arrangement  as  shown  in  Fig.  198.  The  only 
difference  is  that  a  shaft  "E"  and  universal  joints  "F"  (sometimes 
called  alignment  joints)  are  between  the  clutch  and  transmission. 

Because  of  the  special  type  of  transmission  used  on  the  Ford  the 
clutch  and  transmission  are  reversed  but  in  all  other  respects  it  is 
identical  in  its  system  of  power  transmission. 

The  location  and  arrangement  of  the  units  of  power  transmission 
on  a  chain  drive  apparatus  differs  as  shown  in  Fig.  200.  The  differen- 
tial is  now  contained  in  the  same  housing  as  the  transmission.  There 
is  no  drive  shaft  with  universal  joints  between  these  parts.  The 
power  is  transmitted  in  the  usual  way  to  the  transmission  and  then 
direct  to  the  differential.  From  the  differential  it  is  transmitted 
by  jack  shafts  "G"  to  the  sprockets  "H"  and  to  the  wheel  sprockets 
"I"  by  chain  "J." 

227 


228  MOTOR  VEHICLES  AND  THEIR  ENGINES 


Fig.  197 


Fig.  198 


POWER  TRANSMISSION 


229 


Fig.  199 


H 


// 


Fig.  200 


230  MOTOR  VEHICLES  AND  THEIR  ENGINES 


*  J 


G  e 

r-     JSI 


Fig.  201 


f     e 


G  ~         ~  6 


Fig.  202 


•*  x  °g 


POWER  TRANSMISSION  231 

When  the  truck  is  arranged  to  drive  and  steer  with  all  four  wheels 
it  requires  a  different  arrangement  of  the  Power  Transmission  units. 
The  power  must  be  transmitted  not  only  to  the  rear  wheels  but  also 
to  the  front  wheels.  The  general  arrangement  of  the  parts  is  shown 
in  Fig.  201.  In  this  arrangement  the  power  is  transmitted  from  the 
engine  to  the  transmission  "D"  through  the  clutch  "A"  and  shaft 
"B"  with  universal  joints  "C."  The  transmission  instead  of  having 
one  shaft  projecting  to  connect  to  the  drive  shaft  is  so  arranged  that 
there  is  a  shaft  "E"  having  both  ends  " E' "  and  "E""  projecting  and 
offset  slightly  from  the  centre  line  of  the  truck.  From  the  trans- 
mission the  power  is  transmitted  to  the  differentials  "H'"  and  "H"J 
by  drive  shafts  "  F' "  and  "  F"  "  employing  universal  joints  "  G."  From 
the  differentials  the  drive  is  transmitted  to  the  wheels  by  the  axles 
which  employ  universal  joints  at  "  J." 

When  four-wheel  drive  is  employed  with  two-wheel  steering  the 
arrangement  of  parts  is  shown  in  Fig.  202. 

The  power  is  transmitted  from  the  engine  to  the  transmission 
"D"  through  the  clutch  "A,"  shaft  "B,"  and  universal  joints  "C." 
Here  the  construction  differs.  A  differential  "E"  is  driven  by  a 
chain  direct  from  the  transmission,  the  two  forming  a  unit.  From 
this  centre  differential  two  shafts  "E'"  and  "E*"  project  in  opposite 
directions.  These  shafts  are  connected  to  the  differentials  "H'"  and 
"H""  on  the  axles  by  the  drive  shafts  "F'"  and  "F;/"  with  universals 
"G."  The  power  is  transmitted  to  the  wheels  by  the  axles.  The 
front  axle  is  equipped  with  universal  joints  "  J." 

In  the  following  chapters  the  different  units  making  up  the  power 
transmission  system  will  be  discussed  in  the  order  in  which  they  are 
generally  found  on  trucks  and  motor  cars.  The  function,  operation, 
and  different  types  will  be  treated  fully. 


CHAPTER  XXII 


CLUTCHES 

Every  motor  vehicle  propelled  by  a  gasoline  engine  requires  some 
device  to  disconnect  the  engine  from  the  remaining  part  of  the  power 
transmission  system.  The  device  used  to  accomplish  this  is  called  a 
clutch. 

A  clutch  has  one  member  positively  driven  by  the  engine  and  the 
other  attached  to  the  transmission  shaft.  When  these  members  are 
separated  the  engine  will  run  without  driving  the  transmission  shaft 
thus  permitting  the  gears  to  be  shifted  easily.  The  surfaces  of  the 
clutch  members  should  be  of  such  material  that  the  driven  member 
slips  on  the  other  when  pressure  is  first  applied.  As  the  pressure  is 
increased  the  driven  member  is  gradually  brought  to  the  speed  of 
the  other  member  the  slippage  entirely  ceasing  and  the  two  making 
firm  contact.  This  drive  is  accomplished  by  the  friction  between 
the  two  members  which  depends  upon  the  materials  in  contact  and 
the  pressure  forcing  them  together.  This  force  must  be  sufficient 
to  prevent  slipping  when  the  clutch  is  engaged  and  the  surfaces 
must  be  of  such  material  as  to  provide  sufficient  friction  to  carry  the 
load.  The  clutch  must  be  easy  to  operate,  requiring  as  little  exertion 
as  possible  on  the  part  of  the  driver.  It  must  not  take  hold  too 
suddenly  or  it  will  cause  a  jerky  operation  of  the  car  and  put  a 
tremendous  strain  on  the  rest  of  the  power  transmission  units. 
Provision  must  be  made  so  that  the  tension  with  which  the  members 
are  held  in  contact  may  be  varied.  It  is  desirable  to  have  the  driven 
member  as  light  as  possible  so  that  it  will  not  continue  to  rotate  for 
any  length  of  time  after  the  clutch  has  been  disengaged.  Protection 
from  dirt  and  dust  should  be  provided  to  protect  the  friction  material 
from  excessive  wear.  For  this  reason  practically  all  clutches  on 
modern  motor-propelled  vehicles  are  housed. 

When  a  clutch  is  disengaged  the  driven  member  will  continue  to 
spin  due  to  its  inertia.  The  heavier  the  driven  member  the  longer 
this  spinning  will  continue.  When  shifting  gears  it  is  desirable  to 
have  the  speed  of  the  transmission  shaft  reduced  and  a  clutch 
brake  is  often  provided  to  reduce  the  speed  of  the  driven  member. 
This  is  accomplished  by  bringing  this  part  in  contact  with  some 
stationary  part  of  the  car  when  the  clutch  pedal  is  fully  depressed. 
Care  must  be  exercised  not  to  depress  the  foot  pedal  too  far  so  that 

232 


CLUTCHES 


233 


the  clutch  brake  entirely  stops  the  driven  member.  This  would 
cause  the  transmission  shaft  to  be  at  rest,  making  the  shifting  of 
gears  difficult. 

Actual  constructions  of  clutches  vary  on  every  make  of  motor 
vehicle  but  they  may  all  be  grouped  under  three  general  headings; 
cone  clutches  (internal  and  external),  multiple  disc  clutches  (wet 
and  dry),  and  plate  clutches  (wet  and  dry). 


-A- 


Fig.  203— External  Cone  Clutch 

Fig.  203  shows  diagrammatically  an  external  cone  clutch  in  two 
positions.  A  shows  the  clutch  engaged  and  B  shows  it  disengaged. 
The  driving  member  of  the  clutch  is  the  fly  wheel  "F,"  the  inner 
surface  "I"  of  which  is  conically  machined  at  an  angle  of  12°  to  15°. 
The  driven  member  of  the  clutch  is  the  housing  "H"  which  is  lightly 
constructed  and  is  supported  by  a  bearing  on  an  extension  of  the 
crank  shaft.  It  is  conically  shaped  to  fit  perfectly  with  the  inner 
surface  of  the  fly  wheel.  The  conical  surface  is  faced  with  some  high 
friction  material  "R"  such  as  leather  or  Raybestos.  These  surfaces 
"I"  and  "R"  are  forced  together  by  the  action  of  the  spring  "S." 
This  spring  tension  can  be  adjusted  by  nut  "N." 

To  disengage  the  clutch  a  foot  pedal  operated  by  the  driver  is 
provided.  It  is  pivoted  at  "  P  "  and  the  lower  end  is  forked  engaging 
a  yoke  "  Y "  attached  to  the  housing  "  H.' '  When  the  pedal  is  pushed 
forward  it  moves  part  "H"  backward  so  that  the  surfaces  "I"  and 
"R"  are  no  longer  in  contact.  This  permits  the  flywheel  to  revolve 


234 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


Fiy  "WHEEL 

CLUTCH 
CONE 


CLUTCH 
FACING 


CLUTCH 
PEDAL 


EXPANDER-    SPRING 
ADJUSTING   NUT 
THRUST  BEARING 
GREASE  CUP 
RELEASE  RING 
RELEASE  ROD 


independently  of  part  "H;"  thus  the  engine  is  disconnected  from  the 
power  transmission  system.  To  disengage  the  clutch  it  is  necessary 
to  compress  the  spring  "S"  which  requires  considerable  pressure  on 
the  yoke  "Y."  Hence  the  pedal  is  constructed  with  sufficient 
leverage  to  require  little  effort  on  the  part  of  the  driver. 

To  function  properly  the  clutch  should  be  released  gradually. 
This  permits  slipping  between  surfaces  "I"  and  "R"  resulting  in  a 
gradual  application  of  power  to  "H"  until  the  spring  "S"  exerts  its 

full  pressure.  This  forces 
the  two  friction  surfaces 
together  so  that  they 
turn-  as  one. 

Fig.  204  shows  the 
cone  clutch  used  on  the 
Buick  four-cylinder  auto- 
mobile. The  springs 
holding  the  clutch  in  en- 
gagement are  arranged 
differently  from  that 
shown  in  Fig.  203  but 
the  operation  is  identical. 
The  expander  springs  are 
provided  to  press  the 
leather  facing  out  at  sev- 
eral points  and  assure 
gradual  engagement  of 
the  clutch.  This  practise 
is  quite  common  where 
leather-faced  cone  clut- 
ches are  used. 

Fig.  205  shows  dia- 
grammatically  an  inter- 
nal cone  clutch  in  two 
positions.  A  shows  the 
clutch  engaged  and  B 
shows  it  disengaged.  The 
operation  of  this  clutch 
It  is  held  in  engagement 
It 


CLUTCH  GEAR 
RELEASE  YOLK 
CLUTCH  SLEEVE 


Fig.  204— Typical  Cone  Clutch 


is  identical  with  that  of  the  external  type, 
by  the  spring  "S"  and  is  disengaged  by  depressing  the  foot  pedal, 
differs  in  that  the  spring  "S"  is  placed  inside  the  driven  member 
"H."  The  spring  forces  "H"  to  the  rear  to  engage  the  friction 
surfaces  "R"  and  "I."  Adjusting  nut  "N"  regulates  the  tension 
on  the  spring  as  before. 


CLUTCHES 


235 


This  type  was  originally  designed  to  better  protect  the  friction 
surfaces  from  exposure  to  dust  and  dirt  of  the  road.     The  general 


Fig.  205 — Internal  Cone  Clutch 

adoption  of  clutch  housings  has  eliminated  this  design  because  of  the 
difficulty  in  disassembling  it. 

Cone  clutches  are  usually  faced  with  leather.  To  secure  smooth 
action  the  leather  must  be  kept  soft  and  pliable  by  the  frequent 
application  of  Neat's  Foot  oil.  If  this  is  neglected  the  leather  be- 
comes hard  and  dry  resulting  in  " grabbing"  even  when  the  foot  pedal 
is  gradually  released.  This  puts  sudden  strains  on  the  power  trans- 
mission units  causing  the  car  to  operate  jerkily. 

If  oil  or  grease  is  allowed  to  accumulate  on  the  surface  of  a  leather- 
faced  cone  clutch  slipping  will  result  when  the  clutch  is  engaged. 
This  can  be  temporarily  overcome  by  applying  Fuller's  Earth  but 
the  leather  should  be  thoroughly  washed  with  gasoline  and  then 
treated  with  Neat's  Foot  oil  a-t  the  earliest  opportunity. 

Fig.  206  shows  diagrammatically  a  multiple  disc  clutch.  Its 
principle  of  operation  is  the  same  as  that  of  the  cone  clutch.  The 
power  from  the  engine  is  transmitted  to  the  driven  member  by 
friction.  The  friction  surfaces  are  held  in  contact  by  a  spring  "S" 
which  is  released  by  depressing  a  foot  pedal.  The  tension  on  this 
spring  is  adjustable  by  means  of  the  nut  "N."  Shaft  "F"  from  the 
engine  has  plates  or  discs  "R"  keyed  to  it.  Between  these  plates 
are  placed  plates  or  discs  "I"  keyed  to  the  housing  "H"  which  is 


236 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


attached  to  shaft  "T"  running  to  the  transmission.  Both  sets  of 
plates  "R"  and  "I"  are  free  to  move  laterally  but  must  revolve 
with  the  members  to  which  they  are  keyed.  When  the  foot  pedal 
is  released  the  spring  "S"  forces  these  plates  together  and  the  fric- 


Fig.  206— Multiple  Disc  Clutch 

tion  between  them  causes  the  assembly  to  revolve  as  a  unit.  As 
the  clutch  engages  there  will  be  a  slippage  between  the  plates  until 
the  spring  tension  has  forced  all  the  plates  tightly  in  contact. 
When  disengaging  the  clutch  the  spring  is  compressed  and  the 
housing  "H"  is  moved  to  the  rear.  This,  however,  does  not  separate 
the  plates  "I"  and  "R."  Cork  or  spring  inserts  are  often  placed  in 
one  set  of  plates  to  accomplish  this  and  prevent  "  dragging."  In 
some  clutches  both  sets  of  plates  are  of  metal,  one  set  usually  being 
made  of  bronze  and  the  other  of  steel.  This  construction  is  usually 
found  where  the  plates  run  in  oil.  Multiple  disc  clutches  that  run 
dry  generally  have  one  set  of  plates  covered  with  some  high  friction 
material  such  as  Raybestos. 

Fig.  207  shows  the  multiple  disc  clutch  used  on  the  Packard 
Trucks.  It  is  a  dry  clutch  composed  of  two  sets  of  steel  discs.  The 
set  which  is  keyed  to  the  housing  bolted  to  the  fly  wheel  is  faced 
with  special  friction  material. 

Fig.  208  Shows  the  multiple  disc  clutch  used  on  the  F.  W.  D. 
trucks.  This  is  the  Hele*  Shaw  clutch  and  the  discs  run  in  oil.  There 
are  two  sets  of  discs,  one  of  steel  which  is  keyed  to  the  transmission 


CLUTCHES 


237 


Fig.  207— Packard  Clutch 

shaft  and  one  of  bronze  which  is  keyed  to  the  housing  bolted  to 
the  flywheel.  These  discs  are  V-grooved  (Fig.  209)  which  increases 
the  amount  of  friction  surface. 

separate  the  plates  when 
the  clutch  is  disengaged,  dis- 
engaging springs  are  used. 
The  operation  of  this  clutch 
is  identical  with  all  other 
multiple  disc  clutches. 

Fig.  210  shows  diagram- 
matically  a  plate  clutch  in  two 
positions.  A  shows  the  clutch 
engaged  and  B  shows  it  disen- 
gaged. The  principle  of  oper- 
ation of  this  clutch  is  the  same 


Fig.  208— Hele  Shaw  Clutch 


as  that  of  the  cone  clutch.     The  power  of  the  engine  is  transmitted 
to  the  driven  member  by  friction.     The  friction  surfaces  are  held 


Fig.  209— Discs  in  Hele  Shaw  Clutch 

in  contact  by  spring  "S"  which  is  released  by  depressing  the  foot 
pedal.     The  tension  on  the  spring  "S"  may  be  adjusted  by  means  of 


238 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


the  nut  "N."    Between  the  housing  "H"  and  the  machined  face  of 
the  fly  wheel  "I"  is  placed  a  plate  "P"  of  special  friction  material 


Fig.  210— Plate  Clutch 

independent  of  all  moving  parts.     When  the  clutch  is  gradually  en- 
gaged slippage  takes  place  between  the  surface  "R"  and  plate  "P' 


B  U  12131415  B  PBB202 


Fig.  211— Nash  Clutch 

and  surface  "I"  and  plate  "P."     This  permits  a  more  gradual  appli- 
cation -of  power  than  if  the  friction  material  were  fastened  to  either 


CLUTCHES 


239 


the  flywheel  or  housing.  As  the  pressure  of  the  spring  increases 
forcing  the  plate  "P"  and  surfaces  "I"  and  "R"  together  the 
slippage  ceases  and  the  whole  assembly  turns  as  one  unit. 

Plate  clutches  are  sometimes  constructed  with  two  plates  of 
friction  material  separated  by  a  steel  disc  pinned  to  the  flywheel. 
The  increased  surfaces  permit  more  slippage  and  therefore  give  a 
smoother  operating  clutch.  Plate  clutches  are  built  to  run  dry  or  in 
a  bath  of  oil  depending  upon  the  materials  used. 

Fig.  211  shows  the  dry  plate  clutch  used  on  the  Nash  Trucks. 
The  spring  "14"  forces  the  friction  surfaces  "5"  in  contact  with  the 
flywheel.  The  power  of  the  engine  is  transmitted  from  the  fly  wheel 
to  the  drive  plate  "2"  which  is  keyed  to  shaft  "  16"  connected  to  the 
transmission. 

The  White  plate  clutch  runs  in  a  bath  of  light  oil  (Fig.  2.12). 
The  operation  of  this  clutch  is  as  follows:  The  spring  "15"  forces 
housing  "14"  forward  and  in  so  doing  raises  arm  "10"  to  which  are 
attached  the  wedge-shape  pieces  "11."  As  part  "16"  is  stationary 
the  wedge-shape  part  will  force  the  friction  surfaces  together  thus 
permitting  the  flywheel  to  drive  the  friction  plate  "3"  which  is 
bolted  to  the  clutch  shaft  "7"  connecting  with  the  transmission. 


42     39   41    40 


Fig.  212— White  Clutch 

When  the  foot  pedal  is  depressed  the  wedge-shaped  part  "11" 
is  lowered  thus  permitting  the  friction  surfaces  to  separate 
and  the  flywheel  to  turn  without  driving  the  friction  plate  "3." 


240  MOTOR  VEHICLES  AND  THEIR  ENGINES 

There  are  three  general  clutch  troubles;  slipping,  gripping,  and 
dragging. 

Slipping  as  previously  explained  may  result  from  the  condition 
of  the  friction  surfaces.  Dry  clutches  slip  when  too  much  oil  has 
accumulated  on  their  surfaces.  Wet  clutches  sometimes  slip  when 
too  heavy  a  lubricant  is  used  as  the  spring  tension  will  not  be  suffi- 
cient to  force  the  oil  from  between  the  plates.  This  prevents  the 
friction  surfaces  from  coming  intimately  into  contact.  It  is  par- 
ticularly true  of  multiple  disc  clutches.  Slipping  is  usually  the 
result  of  insufficient  spring  tension  since  the  friction  between  the 
surfaces  depends  upon  the  pressure  exerted  by  the  spring.  This  is 
remedied  by  tightening  up  on  the  clutch  adjusting  nut. 

Gripping  may  be  the  result  of  the  condition  of  the  friction  sur- 
faces as  has  already  been  explained  under  cone  clutches.  However, 
it  is  usually  the  result  of  too  much  spring  tension  due  to  the  adjusting 
nut  being  too  tight.  This  nut  should  be  loosened  until  the  proper 
spring  tension  is  obtained. 

Dragging  results  from  the  adjusting  nut  being  so  tight  that  con- 
siderable spring  tension  is  exerted  even  when  the  clutch  pedal  is 
released.  In  a  wet  clutch,  if  the  oil  is  too  heavy  or  is  left  in  the 
clutch  so  long  that  it  becomes  "gummy,"  the  plates  will  adhere  and 
dragging  will  result.  This  is  particularly  true  of  multiple  disc 
clutches.  It  is  remedied  by  washing  out  the  clutch  with  kerosene 
and  refilling  with  proper  lubricant^ 


CHAPTER  XXIII 


TRANSMISSIONS 

An  internal  combustion  engine  does  not  develop  its  full  power  at 
low  speeds,  therefore,  an  automobile  engine  cannot  pull  much  of  a 
load  at  low  speed  and  gears  must  be  interposed  between  the  engine 
and  driving  wheels.  This  permits  the  crank  shaft  to  turn  at  the 
speed  necessary  to  produce  the  desired  power  while  the  wheels  turn 
at  the  speed  the  road  conditions  or  grades  require.  To  secure 
flexibility  of  operation  three  and  sometimes  four  speed  ratios  are 
provided.  To  back  the  car  a  set  of  gears  are  arranged  in  the  trans- 
mission to  reverse  the  direction  of  the  drive  transmitted  to  the  wheels. 
The  gears,  shafts,  and  other  parts  necessary  for  varying  the  forward 
speed  and  obtaining  a  reverse  are  all  contained  in  a  housing  or  gear 
case  and  the  assembly  is  called  a  transmission  although  it  would  be 
more  correct  to  call  it  a  gear  set. 

The  transmission  may  be  located  in  any  one  of  three  places;  as 
part  of  a  unit  with  the  engine  and  clutch,  as  a  separate  unit  between 
the  clutch  and  rear  axle,  or  as  part  of  a  unit  with  the  rear  axle  which 
is  very  rarely  found  on  modern  motor  vehicles. 

Before  taking  up  transmissions  proper,  gears  will  be  briefly 
discussed.  By  the  use  of  gears  a  mechanical  advantage  is  obtained 
permitting  heavy  loads  to  be  lifted  with  the  minimum  amount  of 
power. 

At  A  (Fig.  213)  a  weight  "W"  is  shown  supported  by  a  rope 
wound  about  a  roller  "R."  When  the  crank  "C"  is  turned  the  rope 


Fig.  213 — Mechanical  Advantage  of  Gears 

is  wound  upon  the  roller  lifting  the  weight.     The  amount  of  force 
required  to  lift  the  weight  will  depend  upon  the  length  of  the  crank 


241 


242  MOTOR  VEHICLES  AND  THEIR  ENGINES 

arm  "C"  and  the  diameter  of  the  roller  "R."  At  B  (Fig.  213)  is 
shown  the  same  weight  supported  by  the  rope  wound  on  a  roller 
"R"  of  exactly  the  same  size  but  which  is  made  fast  to  the  large 
gear  wheel  "G."  Meshing  with  "G"  is  a  smaller  gear  or  pinion 
"P"  to  which  is  attached  a  crank  "C"  the  same  length  as  before. 
When  the  crank  is  turned  pinion  "P"  revolves  causing  gear  "G" 
to  revolve  also  and  lift  the  weight  "W"  by  winding  up  the  rope  on 
roller  "R."  The  force  required  to  lift  weight  "W"  in  this  case  will 
be  considerably  less  than  before  because  of  the  gear  reduction  between 
the  crank  "C"  and  roller  "R."  In  both  cases  the  total  work  done 
is  the  same  which  is  lifting  the  weight  through  a  certain  distance.  In 
the  first  case  one  revolution  of  the  crank  winds  one  turn  of  rope  upon 
the  roller  lifting  the  weight  a  corresponding  amount.  In  the  second 
case  one  revolution  of  the  crank  does  not  turn  the  gear  "G"  one 
revolution  because  the  pinion  "P"  can  turn  "G"  only  as  many 
teeth  as  are  on  the  total  circumference  of  "P."  If  the  gear  had 
twice  as  many  teeth  as  the  pinion  two  turns  of  the  crank  would  be 
required  to  revolve  the  roller  once.  Hence,  two  turns  of  the  crank 
at  B  would  lift  the  weight  "W"  only  as  far  as  one  turn  did  at  A, 
but  only  half  as  much  force  (disregarding  friction)  would  be  required. 
It  can  thus  be  seen  that  the  force  necessary  to  do  a  given  amount  of 
work  can  be  reduced  by  the  use  of  gears.  The  reduction  depends 
upon  the  number  of  teeth  on  the  two  gears  in  mesh. 

By  the  use  of  gears  in  the  transmission  an  automobile  engine  is 
able  to  pull  a  heavy  load  up  a  steep  grade.  Their  use  also  explains 
why  the  speed  of  the  machine  decreases  while  the  engine  continues 
to  run  as  fast  or  even  faster  than  before. 

When  two  gears  are  meshed,  one  driving  the  other,  they  will 
rotate  as  shown  in  Fig.  214.  At  A  is  shown  two  spur  gears  in  mesh. 


Fig.  214 — Rotation  of  Gears 

If  "P"  turns  as  indicated  it  will  drive  "G"  in  the  opposite  direction. 
At  B  is  shown  an  internal  gear  and  pinion  in  mesh.     If  "P"  turns  as 


TRANSMISSIONS 


243 


indicated  it  will  drive  "G"  in  the  same  direction.  The  rotation  of 
i ;  combinations  of  more  than  two  gears  such  as  shown  at  C  can  be 
traced  out  the  same  fundamentals  applying. 

The  expression  "gear  ratio"  or  "gear  reduction"  means  the 
relation  between  the  number  of  teeth  on  one  gear  as  compared  to 
I  the  number  on  the  gear  which  is  driven  by  it.  For  example,  if  one 
gear  has  12  teeth  and  drives  a  gear  having  42  teeth  the  gear  ratio  is 
42  to  12  or  3H  to  1.  This  term  will  be  used  throughout  the  fol- 
lowing chapters  on  the  power  transmission  system  wherever  gears 
are  encountered,  hence,  must  be  clearly  understood. 

The  earliest  form  of  transmission  was  a  friction  type  in  which  no 
gears  were  used.  This  gave  unlimited  speed  ratios  between  the 
engine  and  drive  shaft  and  also  eliminated  the  clutch. 


Fig.  215 — Friction  Transmission 

Fig.  215  shows  two  views  of  a  friction  transmission.  The  driven 
wheel  slides  on  a  counter-shaft  and  can  be  shifted  across  the  face  of 
the  driving  disc  and  engaged  at  different  positions  at  varying  dis- 
tances from  its  center.  The  further  the  driven  wheel  is  moved 
toward  the  outer  edge  of  the  disc  the  greater  will  be  its  speed.  For 
example,  the  greatest  speed  will  be  obtained  when  the  wheel  is  in 
position  G  and  the  least  at  position  D.  To  obtain  reverse  the  wheel 
is  simply  shifted  to  the  other  side  of  the  disc  to  some  position  such 
as  C. 

The  drive  is  interrupted  by  moving  the  driving  disc  forward. 
Friction  is  obtained  between  the  driving  disc  and  driven  wheel, 
usually  faced  with  fibre,  by  pressure  exerted  on  the  disc  by  a  spring 
(not  shown).  In  this  way  clutch  action  is  obtained. 

Since  only  a  very  small  amount  of  contact  surface  is  possible 
with  this  transmission  slipping  results  when  heavy  loads  are  pulled. 
This  wears  out  the  friction  surface  rapidly.  A  much  heavier  spring 
than  that  used  for  ordinary  clutches  is  required  since  the  contact 
surfaces  are  smaller.  The  disc  and  wheel  must  be  made  so  large  for 


244  MOTOR  VEHICLES  AND  THEIR  ENGINES 

heavy  pulling  that  the  construction  becomes  cumbersome  making 
its  use  prohibitive  on  all  but  the  lightest  machines. 

To  obtain  positive  transmission  of  power  gear  types  of  transmis- 
sions were  developed.  There  are  three  types  now  in  common  use. 
These  are  the  progressive,  the  selective,  and  the  planetary.  The 
different  gear  ratios  are  obtained  by  bringing  different  combinations 
of  gears  into  action.  In  the  selective  and  progressive  types  this  is 
accomplished  by  shifting  gears  or  dogs. 

The  progressive  type  of  transmission  has  but  one  set  of  sliding 
gears  shifted  by  moving  a  lever  forward  one  notch  for  each  higher 
ratio.  From  the  neutral  position  the  lever  is  moved  straight  back- 
ward for  reverse.  A  typical  three-speed  progressive  gear  set  is  shown 
in  Fig.  216,  the  positions  of  the  gears  when  in  neutral,  low,  second, 
high,  and  reverse  being  shown. 

The  power  of  the  engine  is  transmitted  to  a  short  hollow  shaft 
"A"  called  a  sleeve  which  carries  a  gear  "B"  that  is  in  permanent 
mesh  with  a  gear  "C"  on  the  end  of  the  countershaft.  Parallel  to 
the  countershaft  is  another  shaft,  one  end  of  which  is  supported  by 
a  bearing  in  the  hollow  sleeve.  Though  the  sleeve  supports  this 
shaft  the  two  may  revolve  independently  of  each  other.  The  second 
shaft  is  square  or  of  such  construction  that  the  two  paired  gears 
may  slide  along  but  must  revolve  with  it.  The  gears  on  the  square 
shaft  are  of  different  sizes  and  in  sliding  come  successively  into  mesh 
with  gears  carried  on  the  countershaft.  Because  the  gears  "B"  and 
"C"  are  in  mesh  the  countershaft  revolves  when  the  engine  revolves, 
but  the  speed  of  the  square  shaft  depends  on  the  combination  of 
gears  in  mesh  between  it  and  the  countershaft.  When  the  sliding 
gears  are  in  such  a  position  that  they  are  not  in  mesh  with  the  coun- 
tershaft gears  the  square  shaft  is  independent  of  the  countershaft 
and  may  revolve  or  be  stationary.  The  gears  are  then  in  the  neutral 
position.  When  the  sliding  pair  is  moved  so  that  its  larger  gear  is 
in  mesh  with  the  smallest  of  the  countershaft  gears  "D,"  the  square 
shaft  will  revolve  at  a  slower  speed  than  the  countershaft  because  its 
gear  is  larger  than  the  one  driving  it.  This  is  low  speed  position. 
Again  sliding  the  moving  pair  will  separate  these  gears  and  bring  the 
next  pair  "E"  into  mesh  the  square  shaft  then  moving  at  a  higher 
speed.  It  still  moves  slower  than  the  countershaft  because  of  the 
difference  in  the  size  of  the  gears.  Sliding  the  moving  pair  still 
farther  along  the  shaft  will  disengage  the  second  speed  gears  and 
engage  the  high  speed  in  which  the  square  shaft  revolves  at  the  speed 
of  the  sleeve  and  crank  shaft.  This  is  effected  by  locking  the  moving 
pair  to  the  sleeve  by  means  of  a  dog  "G."  This  dog  consists  of 
several  fingers  projecting  from  the  moving  pair  corresponding  to 


TRANSMISSIONS 


245 


the  spaces  between  similar  fingers  on  the  end  of  the  sleeve.  The 
locking  together  of  the  square  shaft  and  sleeve  gives  direct  drive. 
In  direct  drive  the  power  of  the  engine  is  directly  applied  to  the  square 
shaft  avoiding  the  loss  that  occurs  through  the  friction  of  the  gear 
teeth  at  other  speeds.  The  revolution  of  the  square  shaft  is  trans- 
mitted to  the  driving  wheels,  the  speed  of  the  car  corresponding  to  the 


C  **~\     I  . 'TJ    -rrJU^=. 


Fig.  216 — Progressive  Transmission 

speed  at  which  the  square  shaft  is  driven  by  the  gear  combinations 
between  it  and  the  countershaft. 

To  obtain  the  reverse  which  enables  the  car  to  be  backed  without 
reversing  the  engine,  a  third  gear  "JF  "  is  introduced  between  the  low 
speed  gears  of  the  square  shaft  and  countershaft.  When  the  car  is 


246  MOTOR  VEHICLES  AND  THEIR  ENGINES 

going  forward  the  square  shaft  and  countershaft  revolve  in  opposite 
directions.  When  the  reverse  gear  is  introduced  between  them  the 
square  shaft  is  revolved  in  the  same  direction  as  the  countershaft 
reversing  the  rotation  of  the  driving  wheels. 

This  type  of  transmission  will  rarely  be  found  on  modern  motor 
vehicles,  the  principal  objection  being  that  it  is  necessary  to  pass 
through  one  or  more  gears  in  shifting  from  high  back  to  neutral. 
If  this  shift  is  made  when  the  car  is  in  motion  stripped  gears  may 
result. 

A  modified  form  of  this  type  sometimes  called  a  semi-progressive 
transmission  is  used  on  motor-cycles.  Fig.  217  shows  the  three- 


Fig.  217 — Indian  Motor  Cycle  Transmission 

speed  gear  set  used  on  the  Indian  Motor-Cycle.  The  gears  are 
shown  in  the  neutral  position  which  is  between  the  low  and  inter- 
mediate gears  on  the  countershaft.  Motor-Cycles  not  requiring  a  re- 
verse gear,  intermediate  is  the  only  gear  that  must  be  passed  through 
in  going  into  high  or  back  to  neutral.  This  modified  type  of  pro- 
gressive gear  set  will  generally  be  found  on  modern  motor-cycles. 

The  selective  type  of  sliding  gear  transmission  is  so  called  because 
it  is  possible  to  engage  any  set  of  gears  desired  in  moving  from  the 
neutral  position  without  passing  through  any  other  gears.  Selective 
gear  sets  are  constructed  with  either  three  or  four  speeds  forward 
and  a  reverse. 

Fig.  218  shows  a  typical  three-speed  gear  set  in  which  the  position 
of  the  gears  when  in  neutral,  low,  intermediate,  high,  and  reverse 
are  shown. 


REVERSE  IDLER  GEAR  L~T" 


-B 


NiON  SHAFT  C 


H         1          Ti 
NEUTRAL 


--COUNTER  SHAFT  D 


,F 


FIRST  SPEED 
OR"  LOW" 


SECOND  SPEED  '-_Jj 
OHlNTERMEOIATE 


THIRD  OR 

"HIGH"  SPEED       N 


REVERSE 


Fig.  218 — Selective  Transmission 


247 


248 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


The  revolution  of  the  engine  is  transmitted  to  the  countershaft 
"D"  through  the  gears  "B"  and  "A"  which  are  always  in  mesh. 
All  gears  on  the  countershaft  are  permanently  keyed  to  it.  The  shaft 
"E"  is  supported  at  one  end  by  bearing  in  the  hollow  end  of  the 
shaft  coming  from  the  engine  and  at  the  other  end  by  the  bearing 
where  it  passes  through  the  transmission  case  for  attachment  to  the 
drive  shaft.  The  gears  "F"  and  "G"  are  free  to  slide  along  shaft 
"E"  but  are  forced  to  turn  with  it  because  of  the  keys  on  its  surface. 
Each  of  these  sliding  gears  have  collars  forged  on  them  in  which 
shifter  forks  engage  as  shown  in  Fig.  219. 


Fig.  219— Gear  Shift  Mechanism 

The  movement  of  the  gear  shift  lever  "A"  to  the  right  or  left 
picks  up  one  or  the  other  of  these  forks  shifting  the  particular  gear 
to  which  it  is  attached.  When  the  gear  shift  lever  is  in  neutral  po- 
sition the  gears  will  be  as  shown  in  neutral  (Fig.  218).  If  the  gear 
shift  lever  is  moved  to  the  position  of  first  speed  gear  "G"  will  be 
moved  along  the  shaft  "E"  until  it  meshes  with  gear  "H"  on  the 
countershaft.  If  the  gear  shift  lever  is  now  moved  in  the  opposite 
direction  gear  "G"  will  be  moved  to  the  reverse  position.  In 
changing  from  low  to  reverse,  gear  "G"  passes  through  the  same 
position  it  occupied  on  the  shaft  "E"  when  in  neutral.  If  second 
speed  is  desired  the  gear  shift  lever  must  be  moved  to  the  opposite 
side  of  the  control  sector  (Fig.  219)  and  in  the  opposite  direction  to 
that  in  going  into  first  speed.  This  now  causes  the  gear  "F"  to 
be  shifted  and  it  is  moved  to  the  position  shown  for  second  speed. 
If  direct  drive  is  desired  the  gear  shift  lever  must  be  moved  in  the 
opposite  direction  shifting  gear  "F"  to  the  position  shown  for  high 
speed.  In  going  from  second  to  high  the  gear  "F"  passes  through 
the  same  position  it  occupies  on  the  shaft  "E"  when  in  neutral. 

Fig.  220  shows  a  typical  three-speed  selective  sliding  gear  trans- 
mission which  is  used  on  the  Dodge  Car.  The  exact  location  of  the 


240 


250 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


reverse  idler  pinion  is  clearly  shown  as  is  also  the  bearing  of  the  sliding 
gear  shaft  in  the  hollow  end  of  the  clutch  shaft.  One  feature  of  this 
transmission  is  that  the  countershaft  does  not  revolve  when  running 
on  high  gear.  This  is  because  the  gear  on  the  clutch  shaft  is  shifted 
so  it  does  not  drive  the  countershaft  gear  when  in  high. 


Bait  Bearing 


Countershaft  and  Gears 


Bearings 


Lower  Half  of 
Gear  Case 

Main  Shaft 

Reverse,  I  stand  2nd 
Speed  Shift  Member 

Fig.  221 — White  Transmission 

Fig.  221  shows  the  four-speed  transmission  used  on  the  White 
Motor  Cars.  It  is  identical  with  the  three-speed  transmission  except 
for  the  addition  of  another  set  of  gears.  This  transmission  is  ar- 
ranged so  that  on  third  speed  the  drive  is  direct,  while  on  fourth  speed 
the  drive  shaft  turns  faster  than  the  engine  shaft.  This  arrangement 
permits  increased  speed  with  light  loads.  The  usual  four-speed  con- 
struction especially  for  trucks  has  direct  drive  on  fourth  speed  and 
three  lower  gear  ratios  permitting  greater  flexibility  of  drive.  Se- 
lective sliding  gear  or  sliding  dog  transmissions  are  almost  universally 
used  on  modern  cars  and  trucks,  the  three-speed  type  being  the  most 
common. 

When  heavy  loads  are  pulled  a  considerable  strain  is  put  on  the 
gear  teeth  when  they  are  being  shifted  sometimes  causing  the  teeth 
to  be  stripped  from  the  gear.  To  eliminate  this  trouble  on  heavy 
cars  and  trucks  the  gears  are  placed  permanently  in  mesh,  the  drive 


TRANSMISSIONS 


251 


being  obtained   by   engaging   dogs   or  individual   clutches.     This 
construction  is  especially  desirable  on  four-wheel  drive  trucks. 

Fig.  222  shows  the  selective  sliding  dog  gear  set  used  on  the  F. 
W.  D.  Trucks.  The  gears  on  the  countershaft  and  main  shaft  are 
always  in  mesh.  Shifting  dogs  are  moved  along  the  main  shaft  just 
as  the  gears  are  shifted  hi  ordinary  selective  types  of  transmission. 


Fig.  222— F.  W .  D.  Transmission 


One  feature  of  this  transmission  is  that  when  the  high  speed  dog  is 
shifted  forward  engaging  the  engine  shaft  a  yoke  throws  out  the  dog 
on  the  countershaft  so  that  it  does  not  revolve. 

Fig.  223  shows  the  selective  transmission  used  on  the  Nash 
Trucks.  This  transmission  is  of  the  sliding  dog  type  but  differs  in 
having  dogs  and  gears  integral  with  each  other.  The  shifting  gears 
are  provided  with  clutches  or  dogs  of  four  jaws  and  are  shifted  on 
both  the  countershaft  and  mainshaft.  The  power  from  the  engine  is 
applied  to  the  main  shaft  "4"  called  the  "spline  shaft."  Upon  this 
spline  shaft  and  driven  by  it  are  the  sliding  gears  "10"  consisting  of 
a  unit  of  two  gears  whose  outer  ends  are  provided  with  dogs.  Gear 
"7"  is  free  to  turn  on  the  spline  shaft  and  gear  "11"  is  also  free  to 
turn  on  it  but  is  bolted  to  the  drive  sprocket  "  15."  The  countershaft 
"28"  called  the  "lay  shaft"  carries  the  sliding  gears  "30"  and  "32" 
which  are  provided  with  dogs  and  free  to  turn  on  it.  Gear  "29"  is 
keyed  to  the  lay  shaft  and  in  constant  mesh  with  gear  "7, "  and  gear 
"34"  is  also  keyed  to  the  lay  shaft  and  in  constant  mesh  with  gear 
"11."  The  reverse  gear  shaft  "48"  carries  the  reverse  gears  "50" 
which  may  be  shifted  to  engage  gears  "10"  and  "11." 


252 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


15 


TRANSMISSION  ASSEMBLY 


4— Splineshaft 

7 — Transmission  third-speed  drive  gear 
10 — Transmission  splineshaft  sliding  gear 
11 — Transmission  drive  sprocket  gear 
15 — Splineshaft  drive  sprocket 
28 — Transmission  layshaft 
29— Transmission   layshaft    third- 
speed  gear 


30 — Transmission  layshaft  second-speed  gear 

32 — Transmission  layshaft  first-speed  gear 

34 — Transmission  layshaft  drive  geaf 

41 — Transmission  countershaft 

43 — Countershaft  drive  sprocket 

48 — Reverse  gear  shaft 

50 — Reverse  gear 

51 — Silent  drive  chain 


Fig.  223 — Nash  Transmission 


When  the  gear  shift  lever  is  moved  to  first  speed  position  gear 
"32"  is  shifted  so  its  dogs  engage  those  of  gear  "34."  The  power 
is  now  transmitted  from  the  spline  shaft  by  gear  "10"  to  gear  "32," 
to  gear  "34,"  to  gear  "11,"  and  sprocket  "15,"  through  chain  "51" 
to  the  transmission  countershaft  "41."  When  the  gear  shift  lever 
is  moved  to  the  second  speed  position  the  dogs  of  gears  "32"  and 
"28"  are  disengaged  and  those  of  "30"  and  "29"  are  engaged. 
This  is  accomplished  because  one  shifting  fork  controls  both  gears. 
The  power  is  now  transmitted  from  the  spline  shaft  by  gear  "10" 
to  gear  "30,"  to  gear  "29"  and  shaft  "28,"  to  gear  "34,"  to  gear 
"11,"  and  to  the  counter-shaft  as  before.  In  moving  the  gear  shift 
lever  from  second  to  third  speed  position  the  neutral  position  is 
passed  through  which  disengages  gear  "30."  Gear  "10"  is  moved 
forward  its  dogs  engaging  those  of  gear  "  7."  The  power  is  now  trans- 
mitted from  the  spline  shaft  to  gear  "10"  to  gear  "7,"  to  gear  "29" 


TRANSMISSIONS 


253 


and  shaft  "28,"  to  gear  "34,"  to  gear  "11,"  and  to  the  transmission 
countershaft  as  before.  When  the  gear  shift  lever  is  in  fourth  speed 
position  the  dogs  of  gear  "10"  are  disengaged  from  those  of  gear  "7" 
and  engaged  with  those  of  gear  "11."  The  power  is  now  transmitted 
directly  from  the  spline  shaft  by  the  dogs  of  gear  "  10,"  to  gear  "  11," 
and  to  the  transmission  countershaft  as  before.  When  the  gear  shift 
lever  is  in  reverse  position,  gear  "50"  meshes  with  gear  "10"  and 
the  pinion  paired  with  gear  "50"  meshes  with  gear  "11."  The 
power  is  now  transmitted  from  the  spline  shaft  through  gear  "10," 
to  gear  pair  "50,"  to  gear  "11,"  and  to  the  transmission  countershaft 
as  before,  rotation  being  in  the  opposite  direction. 

The  planetary  transmission  differs  from  the  progressive  and 
selective  types  in  that  the  groups  of  gears  always  remain  in  mesh  and 
revolve  around  a  main  axis.  The  different  sets  of  gears  are  brought 
into  action  by  stopping  the  revolution  of  the  parts  which  support  the 
gears.  To  hold  these  parts  from  revolving  brake  bands  are  com- 
monly used.  In  this  way  a  simple  operating  transmission  can  be 
constructed  having  no  dogs  or  gears  to  be  meshed  when  changing 
speeds. 

To  understand  the  operation  of  the  Ford  Planetary  Transmission 
it  is  necessary  to  know  fully  the  exact  assembly  of  the  parts.  In 


Fig.  224 — Ford  Transmission  Disassembled 

Fig.  224  the  transmission  parts  are  shown  in  their  relative  assembling 
positions  and  the  groups  in  their  different  stages  of  assembling. 

The  first  operation  is  the  assembling  of  group  2  which  is  as  fol- 
lows: Place  the  brake  drum  on  the  table  with  the  hub  in  a  vertical 
position.  Then  place  the  slow-speed  drum  and  gear  over  the  hub 


254  MOTOR  VEHICLES  AND  THEIR  ENGINES 

with  gear  uppermost.  Next  place  the  reverse  drum  over  the  slow 
speed  drum  so  that  the  reverse  gear  is  just  behind  the  slow  speed 
gear.  Then  place  the  driven  gear  in  position  so  that  the  teeth  will 
be  downward  and  key  it  to  the  brake  drum  housing.  The  triple 
gear  should  now  be  meshed  with  the  gears  attached  to  each  of  the 
drums  so  that  the  punch  marks  line  up.  The  gears  should  then  be 
tied  so  that  they  cannot  move. 

The  assembly  should  now  be  placed  on  the  flywheel  as  shown  in 
group  3  so  that  the  triple  gears  fit  on  the  triple  gear  pin  and  the  trans- 
mission shaft  extends  beyond  the  inner  face  of  the  brake  drum. 
The  clutch  drum  key  should  be  fitted  in  the  transmission  shaft  so 
that  it  will  hold  the  clutch  drum  rigid  to  it  when  put  in  place.  The 
clutch  drum  should  next  be  placed  on  the  transmission  shaft  and  the 
set  screw  fastened.  The  clutch  plates  should  next  be  placed  over 
the  clutch  drum.  Put  a  large  disc  on  first  then  a  small  disc  alter- 
nating with  large  and  small  discs  until  the  entire  set  is  assembled  in 


Fig.  225 — Assembled  Transmission 

position.  The  large  discs  are  keyed  to  the  brake  drum  and  the  small 
discs  are  keyed  to  the  disc  drum  so  that  they  must  revolve  with  the 
parts  to  which  they  are  keyed  but  can  be  moved  backward  or  for- 
ward. Next  put  the  clutch  push  ring  in  place  and  attach  the  driving 
plate  to  the  brake  drum  so  that  the  studs  on  the  clutch  push  ring 
press  against  the  clutch  fingers.  Then  place  the  clutch  shift,  clutch 
spring,  and  clutch  spring  support  in  place  and  fasten  with  clutch 
spring  and  support  pin.  The  assembly  is  now  complete  (Fig.  225). 
Fig.  226  shows  the  pedals  and  brake  bands  attached  in  their  proper 
places. 


Fig.  226— Control  Pedals 

Fig.  227  shows  diagrammatically  the  arrangement  of  the  parts  of 
the  Ford  Planetary  Transmission  in  cross  section  and  will  be  used  to 
explain  its  operation. 


Fig.  22? — Sectional  Diagram  of  Ford  Transmission 

HIGH  SPEED.— When  the  foot  clutch  pedal  is  released  it  allows 
collar  "  C  "  to  force  arms  "  A  "  forward.  This  forces  the  plates  of  the 
clutch  together  so  that  the  shaft  "S"  and  housing  "B"  are  driven 
as  one  unit.  Every  time  the  flywheel  "F"  makes  one  revolution  the 
housing  "B"  also  makes  a  complete  revolution.  In  this  manner 
drive  is  obtained,  the  entire  transmission  revolving  as  one  unit  and 
the  drive  is  taken  through  the  clutch.  At  all  other  speeds  the  clutch 


256  MOTOR  VEHICLES  AND  THEIR  ENGINES 

is  out  of  operation  and  the  clutch  pedal  must  be  depressed  slightly 
to  free  it. 

SLOW  SPEED.— When  the  clutch  pedal  is  depressed  all  the  way 
it  not  only  releases  the  clutch  but  causes  a  brake  band  to  hold  fast 
the  drum  "L." 

As  the  flywheel  from  which  project  the  studs  carrying  the  triple 
gears  (Fig.  227)  revolves  it  will  be  necessary  for  the  gears  to  revolve 
on  their  own  axes.  Assuming  gear*"l"  has  20  teeth  and  gear  "2" 


A  B 

Fig.  228 — Diagram  Explaining  Operation  of  Transmission 

has  30  teeth  (Fig.  228  A)  the  operation  will  be  as  follows:  As  the 
gear  attached  to  "L"  is  held  stationary  by  the  brake  band,  gear  "2" 
which  is  in  mesh  with  it  will  have  to  roll  on  gear  "L."  When  gear 
"2  "  has  rolled  30  teeth  to  position  X  it  will  have  turned  one  complete 
revolution.  As  gear  "2"  turns  one  complete  revolution  gear  "1" 
must  also  turn  one  complete  revolution.  Assuming  that  it  rolls  on 
gear  "B"  it  would  roll  20  teeth  to  a  position  Y,  This  cannot  be 
true  for  the  triple  gear  pinion  has  to  be  at  X,  therefore,  gear  "1" 
must  drag  gear  "  B  "  with  it  the  distance  from  Y  to  X.  When  driving 
in  high,  gear  "B"  turns  at  the  same  speed  as  the  flywheel.  Now  it 
does  not  turn  as  fast  thus  giving  low  speed. 

REVERSE. — In  this  position  the  clutch  pedal  is  pressed  just  far 
enough  to  release  the  clutch.  The  reverse  foot  pedal  is  pressed  all 
the  way  down.  This  contracts  a  brake  on  the  drum  "R"  (Fig.  227). 
As  the  flywheel  revolves  carrying  with  it  the  triple  gears  the  following 
condition  will  result.  As  the  gear  attached  to  "R"  is  held  stationary 
the  triple  gears  will  have  to  revolve  on  their  own  axes  causing  gear 
"3"  to  roll  on  gear  "R"  (Fig.  228  B).  Assuming  that  gear  "3"  has 


TRANSMISSIONS  257 

10  teeth  it  will  turn  one  revolution  when  it  has  rolled  10  teeth  on 
"R"  and  will  be  at  position  Z.  At  the  same  time  gear  "  1 "  will  have 
to  revolve  one  revolution.  Assuming  that  it  can  roll  at  the  same  time 
on  gear  "B"  it  would  be  at  position  X  when  it  had  turned  one  revo- 
lution. As  it  cannot  be  there  but  must  be  at  position  Z  since  "B" 
is  free  to  move  and  "R"  is  not  it  will  have  to  turn  "B  "  through  the 
distance  from  Y  to  Z.  This  turns  "B"  in  the  reverse  direction  and 
at  a  slower  rate  of  speed  than  the  engine. 

It  must  be  remembered  that  low  and  reverse  speeds  are  de- 
pendent upon  the  brakes  holding  the  bands  fixed  assuming  that  the 
housing  "B"  is  free  to  move.  This  is  not  exactly  true  as  the  weight 
in  driving  the  car  forms  a  brake  on  "B"  thus  tending  to  hold  it 
fixed.  The  brakes  on  the  drums  "R"  and  "L,"  therefore,  must  be  in 
very  good  condition  for  they  must  have  a  greater  braking  force  than 
that  applied  by  the  weight  of  the  car  and  friction  of  the  working 
parts  of  the  power  transmission  units,  or  else  the  drums  will  slip 
under  the  brake  bands  and  a  loss  of  developed  power  to  the  drive 
wheels  will  result. 


CHAPTER  XXIV 


DRIVES 

From  the  transmission  or  gear  set  the  power  must  next  be  de- 
livered to  the  differential  and  thence  to  the  wheels.  It  is  desirable 
to  do  this  in  the  most  efficient  manner  by  reducing  frictional  losses 
to  a  minimum,  yet  the  method  of  drive  employed  must  have  sufficient 
flexibility  to  allow  for  the  movement  of  the  frame  up  and  down  on 
the  springs.  The  usual  method  is  by  a  shaft  from  the  transmission 
direct  to  the  differential.  In  some  cases  where  the  differential  is  not 
placed  on  the  rear  axle  the  final  drive  to  the  wheels  is  made  by  chains. 

When  a  shaft  drive  is  used  universal  joints  are  necessary  to  secure 
the  required  flexibility.  Fig.  229  shows  a  typical  universal  joint. 


Fig.  229— Universal  Joint 

By  being  pivoted  so  its  parts  can  turn  about  axes  perpendicular  to 
each  other  one  member  of  the  joint  may  remain  rigid  while  the  other 
moves  through  variable  angles.  This  ability  of  a  universal  joint  to 
adjust  itself  to  transmit  power  through  variable  angles  makes  it 
applicable  to  shaft  drives. 

One  or  more  universal  joints  must  be  incorporated  in  the  drive 
from  the  transmission  to  the  differential.  This  gives  the  necessary 
flexibility  to  compensate  for  the  movement  of  the  rear  axle  due  to 
spring  action.  Universal  joints  are  always  used  at  points  where  the 

258 


DRIVES 


259 


drive  is  transmitted  by  shafts  at  variable  angles.  Referring  to 
chapter  22  the  power  transmission  charts  show  universal  joints 
used  at  the  following  points:  Between  the  clutch  and  transmission  to 
relieve  any  strains  occasioned  by  twisting  the  frame,  on  drive  shafts 
as  just  explained,  on  axles  whose  wheels  are  both  driven  and  steered 
to  permit  the  wheels  to  turn. 

The  drive  shaft  may  be  tubular  which  gives  it  greater  strength 
and  stiffness  without  excessive  weight.  It  often  is  enclosed  in  an 
extension  of  the  rear  axle  housing  or  it  may  be  exposed. 


Fig.  230 — Enclosed  Drive  Shaft 

Fig.  230  shows  the  enclosed  drive  shaft  used  on  the  Dodge  Car. 
A  construction  of  this  kind  is  advantageous  since  it  protects  the 
moving  parts  and  at  the  same  time  takes  any  possible  strain  on  the 
shaft  other  than  that  of  driving  the  car. 


Fig.  231— Method  of  Drive 

Fig.  231  shows  the  usual  arrangement  of  the  power  transmission 
units  employed  on  shaft  drive  machines.     There  is  less  loss  of  power 


260 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


due  to  angularity  at  the  universal  joints  and  less  wear  when  the 
units  are  nearly  in  alignment. 

In  addition  to  universal  joints  a  sliding  or  telescopic  joint  must 
be  provided  at  some  point  between  the  transmission  and  rear  axle 
due  to  the  slight  variations  in  the  distance  between  them  as  the 
frame  moves  up  and  down.  This  joint  is  many  times  overlooked 
and  its  lubrication  often  neglected. 

The  drive  shaft  transmits  power  to  the  housing  carrying  the  dif- 
ferential gears  through  a  pair  of  bevel,  helical,  or  worm  gears.  In 
each  case  the  pinion  (small  gear)  or  worm  is  keyed  to  the  shaft  and 
meshes  with  the  large  driving  gear  or  worm  wheel  bolted  to  a  flange  on 
the  differential  housing. 

Fig.  232  shows  the  bevel  gear  drive  used  on  the  Ford  car.  The 
drive  shaft  on  which  is  keyed  the  pinion,  meshes  with  the  large  drive 


Fig.  232— Bevel  Gear  Drive 

gear  (ring  gear)  bolted  to  the  differential  housing.  When  the  shaft 
rotates  the  drive  gear  is  caused  to  revolve,  turning  the  axles,  and  in 
this  way  the  drive  is  transmitted  to  the  wheels.  There  is  considerable 
gear  reduction  at  the  rear  axle,  for  the  large  bevel  gear  turns  one  re- 
volution to  every  three  (or  more)  revolutions  of  the  pinion.  Hence, 
the  drive  shaft  turns  at  several  times  the  speed  of  the  axles,  which 
correspondingly  decreases  the  power  required  to  drive  the  wheels. 
This  is  generally  called  " differential  reduction"  and  will  depend  upon 
the  power  required. 


DRIVES 


261 


Fig.  233  shows  the  helical  or  spiral  bevel  driving  gears.  The  an- 
gular cut  teeth  eliminate  backlash  and  play  between  the  teeth  insuring 
quiet  operation.  In  addition, 
continuous  driving  action  re- 
sults, at  least  two  teeth  being 
partly  engaged  at  all  times, 
overcoming  any  tendency  to 
wear  irregularly.  This  type  of 
gear  is  rapidly  replacing  the  or- 
dinary bevel  gear,  with  its  single 
tooth  contact. 

Fig.  234  shows  a  typical 
worm  drive.  The  worm  is 
keyed  to  the  drive  shaft  and 
placed  above  the  gear  wheel 
which  is  the  ordinary  arrange- 
ment. Several  teeth  are  in 
mesh  at  once  resulting  in  quiet 
and  continuous  operation.  The 
gear  wheel  is  usually  made  of 
steel  and  the  worm  of  bronze  to 
reduce  friction  to  a  minimum. 
Because  of  the  large  gear  re- 
ductions obtainable  with  this 
type  of  drive  it  is  particularly 
well  suited  for  trucks  where  a 
differential  reduction  of  be- 
tween 7  and  9  to  1  is  desired. 

To  obtain  a  large  differential 
reduction  on  heavy  trucks, 
chains  are  used  for  the  final  drive.  Fig.  200  shows  a  typical 
arrangement  of  chain  drive.  The  differential  is  generally  housed 
with  the  transmission  gears  and  jack  shafts  drive  chains  by  means 
of  sprockets  on  their  ends.  A  dead  axle  is  used  and  the  wheels 
carry  sprockets  of  larger  diameter  than  those  used  on  the  jack  shafts. 
This  permits  an  additional  reduction  to  that  obtained  at  the  differ- 
ential. When  a  chain  drive  is  used,  universal  joints  are  not  neces- 
sary unless  used  between  the  clutch  and  transmission,  since  the 
chain  is  flexible  and  adjusts  itself  to  the  movement  of  the  frame 
up  and  down  on  the  springs.  A  chain  drive  is  objectionable, 
because  it  is  noisy  and  wears  excessively,  being  exposed  to  the  dust 
and  dirt  of  the  road. 


Fig.  233— Helical  Gear  Drive 


262 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


A  chain  tends  to  pull  the  rear  axle  forward  since  all  the  power  is 
delivered  by  the  pull  of  the  chains  on  the  sprockets.  To  keep  the 
rear  axle  from  being  twisted  out  of  place,  and  also  to  adjust  the  ten- 
sion on  the  chain,  radius  rods  are  used.  These  are  attached  by  flexi- 


Fig.  234 — Worm  Gear  Drive 

ble  couplings,  usually  ball  joints,  to  the  frame  and  axle  and  their 
length  is  adjustable.  In  this  way  the  driving  strain  is  transmitted  to 
the  frame. 

On  shaft-driven  machines  the  driving  strain  is  transmitted  to  the 
frame  through  torque  arms,  radius  rods,  torque  tubes,  distance  rods, 
or  the  springs.  The  torque  arm  is  more  common  on  heavy  cars  and 
the  torque  tube  on  lighter  machines,  it  generally  being  the  extension 
of  the  rear  axle  housing  covering  the  drive  shaft.  Where  the  Hotch- 
kiss  Drive  is  used  (drive  taken  through  the  springs),  the  main  spring 
leaf  is  made  extra  heavy  to  take  this  additional  strain. 


CHAPTER  XXV 


DIFFERENTIALS 

m  a  car  travels  around  a  corner  the  distance  traveled  by  the 
outside  wheels  is  greater  than  that  traveled  by  the  inside  wheels.  If 
the  wheels  are  mounted  on  dead  axles  so  that  they  turn  independently 
of  each  other,  like  the  front  wheels  on  an  ordinary  passenger  vehicle, 
they  will  turn  at  different  speeds  to  compensate  for  the  difference  in 
travel.  If  the  wheels  are  positively  driven  by  the  engine,  a  device  is 
necessary  which  will  permit  them  to  revolve  at  different  speeds  with- 
out interfering  with  their  driving  the  car.  To  accomplish  this  a 
system  of  gears  called  the  differential  is  provided. 


Fig.  235 — Differential  Action  Explained 

The  action  of  the  simple  differential  is  shown  in  Fig.  235.  At 
A  two  shafts  "K"  and  "K-l"  are  attached  to  the  large  bevel  gear 
wheels  "H"  and  "H-l"  and  meshing  with  them  is  the  pinion  "G" 
attached  to  the  shaft  "F."  When  the  shaft  "F"  is  pulled  forward 
as  shown,  but  not  rotated  about  its  axis,  the  pinion  "G"  will  not  re- 
volve. Since  it  is  meshed  with  both  gear  wheels  "H"  and  "H-l" 
they  will  be  turned  about  their  axes,  causing  the  shafts  "K"  and 
"K-l "  to  revolve  equally  and  in  the  same  direction  that  the  shaft  "F" 
is  being  pulled.  The  pinion  "G"  merely  acts  as  a  connection  or 
clutch  between  the  two  gear  wheels.  If  the  axle  "K"  is  held  sta- 
tionary (Fig.  235B),  its  gear  wheel  "H"  cannot  revolve  when  the 
shaft  "F"  is  pulled  forward  as  before.  This  causes  the  pinion  "G" 

263 


264 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


to  roll  on  the  gear  "H"  revolving  about  its  axis,  while  "H-l" 
turns  at  a  greater  speed  than  before.  This  is  because  it  is  forced 
to  revolve  at  the  speed  with  which  shaft  "F"  is  pulled  for- 
ward plus  the  speed  imparted  to  it  by  the  pinion  "G"  revolving 
on  its  own  axis.  Shaft  "  K-l "  still  revolves  in  the  same  direction  that 
shaft  "F"  is  being  pulled.  If  shaft  "K"  is  allowed  to  slip  a 
little  (Fig.  235C)  so  that  it  revolves  in  the  same  direction  as  at  A 
but  not  nearly  so  much,  as  indicated  by  the  arrow,  the  amount  that 
pinion  "G"  rolls  on  the  gear  "H"  will  be  correspondingly 
reduced.  Shaft  "K-l"  will  be  driven  as  before  by  both  the  pull 
on  "F"  and  the  turning  of  the  pinion  "G"  on  its  axis.  Therefore, 
the  pinion  "G"  will  not  revolve  as  much  as  it  did  before,  since  gear 
"H"  is  now  also  turning  correspondingly,  reducing  the  amount  that 
the  shaft  "K-l"  revolves. 

This  is  the  principle  upon  which  all  differentials  are  built,  different 
arrangements  of  gears  being  used  to  accomplish  this  same  result.  In 
the  differential,  the  shafts  "K"  and  "K-l "  are  the  axles  to  which  the 
wheels  are  attached,  either  one  of  which  may  revolve  slower  than  the 
driving  speed.  The  revolution  of  the  other  increases  a  corresponding 
amount  due  to  the  differential  action  of  the  gears. 


Fig.  236— Bevel  Gear  Differential 


DIFFERENTIALS 


265 


Fig.  236  shows  diagrammatically  a  simple  bevel  gear  differential . 
The  pinion  "G"  is  mounted  on  a  short  axle  or  stud  "F"  which  is 
carried  by  a  differential  housing  "E. "  This  housing  is  driven  by  the 
rear  axle  drive  in  this  case,  bevel  gears  "  C  "  and  "  B  "  being  employed. 
When  the  gear  wheel  "C"  turns  in  the  direction  shown  the  differential 
housing  turns  with  it,  carrying  the  stud  "F"  and  pinion  "G"  in  just 
the  same  way  as  when  the  shaft  "F"  was  pulled  over  by  hand.  Any 
difference  in  the  rotation  of  the  rear  wheels  is  compensated  for  by  the 
rotation  of  the  differential  pinion  "G"  on  the  stud  "F"  while  re- 
volving bodily  about  the  axis  "X-Y."  If  the  pinion  "G"  rotates,  it 
must  roll  on  one  of  the  differential  gears  "H"  or  "H-l"  and  the 
amount  of  motion  in  rolling  on  the  one  gear  is  transmitted  to  the 
other  as  an  additional  turning  or  driving  effort.  Any  retarded 
motion  of  one  wheel  results  in  an  accelerated  motion  of  the  other. 
The  rotation  of  the  engine  is  thus  transmitted  to  the  rear  wheels  in 
proportion  to  the  distance  each  wheel  travels. 

In  Fig.  236  only  one  pinion  is  shown  and  the  differential  housing  is 
merely  a  frame  bolted  to  the  main  driving  gear.  In  actual  differentials 
several  pinions  are  employed  and  the  differential  housing  usually 
partially  encloses  the  differential  gears.  There  are  three  general 
types  of  differential  gears  employed  on  modern  motor  vehicles.  These 
are  the  bevel  gear,  the  spur  gear,  and  the  worm  gear  types  of  differen- 
tials. 


Fig.  237 — Ford  Differential 


Fig.  237  shows  a  typical  bevel  gear  differential.  Both  the  differen- 
tial gears  and  driving  gears  are  clearly  shown.     The  differential 


266 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


housing  can  be  seen  attached  to  the  main  driving  gear  and  carrying 
the  differential  pinions. 

The  objection  to  the  bevel  gear  differential  is,  that  whichever 
wheel  offers  the  least  resistance  is  turned  the  fastest  causing  a  loss  of 
traction.  If  one  wheel  gets  in  the  mud  or  loose  dirt  or  sand,  the 
wheel  on  solid  ground  will  not  be  driven  while  the  other  spins  around 
due  to  the  differential  action. 

The  bevel  gear  differential  was  the 
first  type  developed,  but  the  spur  gear 
differential  will  be  found  on  many 
modern  cars.  Fig.  238  shows  a  spur 
gear  type  of  differential.  The  axle  gears 
are  spur  gears  instead  of  bevel  gears 
and  the  bevel  pinion  is  replaced  by  two 
spur  pinions  meshing  with  each  other 
at  their  inner  ends.  Their  outer  ends 
mesh  with  and  drive  the  spur  gears  on 
the  axles,  the  pinions  revolving  on  the 
studs  carried  by  the  differential  housing 
which  is  driven  by  rear  axle  driving 
gears  as  before.  The  pinions  in  this 
case  revolve  parallel  to  the  axle  instead 
of  at  right  angles  to  it  as  in  the  bevel 
gear  type. 


Fig.  23S—Spur  Gear 
Differential 


If  the  pinions  were  long  enough  to  mesh  with  both  the  axle  gears 
and  not  with  each  other,  driving  the  differential  housing  would  cause 
them  to  roll  on  the  axle  gears  all  rotating  on  their  studs  in  the  same 
direction  the  axle  gears  remaining  stationary.  By  meshing  them 
with  each  other  they  cannot  revolve  in  the  same  direction  for  when 
two  gears  are  in  mesh  they  must  revolve  in  opposite  directions.  This 
prevents  the  pinions  from  rolling  around  on  the  axle  gears  when  the 
housing  is  revolved  and  as  long  as  there  is  equal  resistance  on  both  the 
wheels  they  will  not  revolve  on  their  studs,  but  will  act  as  a  lock  or 
clutch  between  the  two  axle  gears  carrying  them  around  with  the 
housing  as  in  the  bevel  gear  type  and  having  the  same  disadvantages. 

If  the  machine  is  turning  a  corner  the  greater  distance  traveled 
by  the  outside  wheel  will  cause  the  pinions  to  revolve  on  their  studs 
permitting  one  differential  gear  to  turn  faster  than  the  other.  This  is 
identically  the  same  action  as  is  obtained  by  the  use  of  bevel  gears. 

Fig.  239  shows  the  worm  gear  differential  which  is  used  on  the  Nash 
Quad  Trucks.  This  differential  is  made  with  two  pinions  "C" 
mounted  in  the  differential  housing  "H"  which  is  rotated  by  the 
driving  gears.  The  two  crown  wheels  "A"  and  "A-l"  are  attached 


DIFFERENTIALS 


267 


to  the  shafts  driving  the  wheels.  Between  the  crown  wheels  "A" 
and  the  pinion  "  C  "  the  worm  gears  "  B  "  are  interposed.  The  worms 
"B"  are  mounted  with  their  axles  at  right  angles  to  those  of  the 
pinion  "C."  When  housing  "H"  is  revolved  it  will  carry  with  it 


H 


Fig.  239— M.  and  S.  Differential 

the  pinion  "  C  "  and  worm  gears  "  B. "  If  the  car  is  traveling  straight 
ahead  these  gears  will  not  revolve  on  their  own  axes  and  the  movement 
of  "A"  and  " A-l "  will  be  the  same.  Assuming  that  gear  "A-l"  was 
held  stationary,  worm  gear  "B"  would  roll  on  it.  The  worm  gear 
"B"  in  turn  would  drive  pinion  "C,"  but  this  is  not  possible  since 
pinion  "C"  cannot  drive  the  other  worm  gear  "B"  which  is  in  mesh 
with  crown  wheel  "A."  If  the  pitch  is  less  than  45  degrees  a  pinion 
cannot  turn  a  worm  gear  but  the  worm  can  turn  the  pinion.  This  is 
the  principle  upon  which  this  differential  is  constructed  As  explained, 
if  one  wheel  is  stationary  and  the  other  free,  the  differential  action 
would  be  locked  and  the  free  wheel  would  not  spin.  When  turning  a 
corner  the  action  is  as  follows :  "A-l"  or  "  A "  being  driven  at  a  greater 


268 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


speed  than  the  other  permits  the  gear  "B  "  which  is  in  mesh  with  it  to 
roll  on  its  surface.  The  one  traveling  faster  will  cause  the  gear  "  B  "  in 
mesh  with  it  to  turn  on  its  axis,  this  movement  being  adjusted  by  the 
pinion  gear  "C."  From  this  it  is  seen  that  a  differential  of  this  con- 
struction is  desirable.  In  case  the  car  is  ditched,  the  wheel  which  is 
free  will  not  have  all  the  turning  transmitted  to  it  thus  making  it 
possible  to  pull  out. 


Fig.  240— Differential  Lock 


When  bevel  or  spur  differentials  are  employed  a  differential 
locking  system  is  used.  Fig.  240  shows  diagrammatically  the  differ- 
ential lock  used  on  the  F.  W.  D.  trucks.  A  dog  is  shifted  on  the 
axle  shaft  so  that  it  engages  or  locks  with  the  differential  housing. 
This  prevents  the  differential  pinions  from  turning  and  the  whole 
system  of  gears  turns  as  a  unit.  In  this  way  the  two  drive  shafts 
revolve  equally  causing  both  front  and  rear  wheels  to  be  driven. 

When  both  the  front  and  rear  wheels  are  driven  a  differential 
must  be  placed  on  the  front  axle  as  well  as  the  rear.  When  a  four- 
wheel  drive  truck  is  steered  by  turning  both  the  front  and  rear  wheels, 
as  is  done  on  the  Nash  Quad  Trucks,  both  front  and  rear  inside  wheels 
will  travel  the  same  distance  in  turning  a  corner  as  will  both  front  and 
rear  outside  wheels.  This  is  because  the  rear  wheels  follow  in  the 
tracks  of  the  front  wheels. 


DIFFERENTIALS  269 

When  only  the  front  wheels  are  steered  on  a  four-wheel  drive 
truck  such  as  the  F.  W.  D.  the  front  and  rear  wheels  do  not  track 
when  turning,  the  rear  wheels  cutting  the  corner.  Therefore  the 
drive  shaft  driving  the  front  wheels  must  turn  at  a  greater  speed 
than  that  driving  the  rear  wheels  which  necessitates  a  third  differen- 
tial being  placed  between  them.  This  is  usually  enclosed  in  a  housing 
bolted  to  the  transmission  and  driven  by  a  chain  from  the  main 
transmission  shaft.  A  typical  construction  of  this  kind  is  shown  in 
Fig.  222. 


CHAPTER  XXVI 


RUNNING  GEAR 

The  parts  of  a  motor  vehicle  not  included  in  developing  and 
transmitting  power  are  classified  under  the  general  heading  of  run- 
ning gear.  This  includes  such  parts  as  frames,  springs,  axles,  wheels, 
brakes,  steering  gear,  etc. 

FRAMES  ] 

The  frame  is  the  skeleton  of  the  motor  vehicle  to  which  all  other 
parts  are  directly  or  indirectly  attached.  Most  frames  manufac- 
tured for  trucks  and  cars  employ  pressed  steel  side  members  which 
are  of  channel  section.  The  cross  members  and  side  members  are 
riveted  in  order  to  make  tight  joints  and  reinforcing  plates  are  used 
to  secure  additional  stiffness.  Such  parts  as  spring  hangers  are 
riveted  to  the  frame.  The  side  members  are  built  with  sufficient 
depth  at  the  center  to  carry  the  load  between  the  axles  without 
bending  and  in  some  cases  truss  rods  are  used  on  cars  or  heavy  trucks 
having  long  wheel  bases.  Since  there  is  a  tendency  to  bend  the 
frame  at  the  center  the  top  part  of  the  channel  members  will  be  under 
compression.  For  this  reason  holes  must  not  be  drilled  in  the  top 
part  of  frames  since  these  would  weaken  the  members  at  the  point  of 
greatest  stress,  often  resulting  in  sagging  or  complete  buckling. 

In  addition  to  the  cross  members  bracing  the  frame  they  often 
support  a  sub-frame  to  which  the  engine  and  sometimes  the  trans- 
mission are  bolted.  This  gives  the  necessary  flexibility  of  support 
for  these  units  reducing  the  distortion  due  to  uneven  roads  to  a 
minimum.  Sub-frames  are  not  necessary  when  unit  power  plants 
are  used  supported  by  the  main  frame  at  three  points. 

SPRINGS 

The  frame  is  attached  to  the  axles  by  springs  which  reduce  the 
road  shock  transmitted  to  the  axles  by  the  wheels  thus  protecting 
the  units  supported  directly  by  the  frame.  It  is  necessary  that  the 
springs  be  both  strong  and  resilient  and  for  this  reason  the  built  up 
or  laminated  leaf  spring  is  universally  used  on  motor-propelled 
vehicles. 

270 


RUNNING  GEAR 


271 


The  action  of  the  spring  leaves  may  be  compared  to  a  deck  of 
cards.  When  held  at  the  center  and  the  ends  bent  up  the  cards  slip 
on  each  other.  The  outer  cards  slip  the  most  since  they  must  con- 
form to  a  curve  of  greater  circumference  than  the  inner  ones.  When 
the  pressure  on  the  ends  of  the  deck  is  released  the  cards  spring  back 
to  their  original  position.  If  a  solid  piece  of  card-board  of  the  same 
size  as  the  deck  were  used  bending  would  cause  it  to  buckle,  since  its 
layers  could  not  slip  on  each  other.  Therefore,  the  flexibility  of  a 
spring  depends  upon  the  number  of  leaves  composing  it  and  when 
pressure  is  applied  at  its  ends  the  leaves  slip  on  each  other  to  conform 
to  the  changed  radius  of  curvature.  For  this  reason  some  lubricant 
must  be  placed  between  the  spring  leaves. 


Fig.  241— Semi-Elliptical  Spring 

The  semi-elliptical  spring  (Fig.  241)  is  clamped  at  its  center  "A" 
to  the  axle  by  a  spring  saddle  clip.  One  end  of  the  spring  is  generally 
bolted  to  the  frame  as  at  "B"  while  the  other  end  is  attached  by 
means  of  a  spring  shackle  which  allows  it  to  move  sufficiently  to 
compensate  for  the  elongation  of  the  spring  when  compressed. 


Fig.  242 — Three-Quarter  Elliptical  Spring 

The  three-quarter  elliptical  spring  (Fig.  242)  is  clamped  to  the 
axle  in  the  usual  manner  at  "A."     One  end  is  bolted  to  the  frame  at 


272 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


"C"  the  other  being  rigidly  held  by  spring  saddle  clips  to  the  frame 
"D."      A  spring  shackle    bolt   "B"   holds  the   two  members  of 

the  spring  together  allowing 
enough  movement  to  com- 
pensate for  the  elongation  of 
the  main  leaves  when  the 
spring  is  compressed. 

The  full  elliptical  spring 
(Fig.  243)  is  attached  rigidly 
to  both  the  axle  and  frame  at 
points  "A"  in  the  usual  man- 
ner. Spring  shackles  are  not 
necessary  since  both  top  and 


Fig.  243 — Full  Elliptical  Spring 


bottom  members  will  elongate 
the  same  amount  when  com- 
pressed.    This  type  of  spring  is  little  used  on  automobiles  because 
the  springs  cannot  be  used  to  transmit   the  driving  effort  to  the 
frame  due  to  their  method  of  attachment. 


Fig.  244— Platform  Springs 

The  platform  spring  construction  (Fig.  244)  is  a  combination  of 
three  semi-elliptical  springs  arranged  as  shown  and  used  for  attaching 
the  frame  to  the  rear  axle  only.  The  front  ends  of  the  two  lower 
springs  are  bolted  to  the  frame  as  at  "C"  their  rear  ends  being 
attached  to  the  third  spring  by  the  double  shackles  or  ball  and  socket 
connections  "B."  This  spring  is  rigidly  fastened  to  the  frame  at 
the  center  of  the  rear  cross  member  "E." 


Fig.  245— Cantilever  Spring 


RUNNING  GEAR 


273 


Fig.  245  shows  a  cantilever  type  of  spring.  It  does  not  differ 
much  from  the  semi-elliptical  spring  in  construction  being  built  up 
in  the  same  way,  but  made  flatter  and  heavier.  However,  it  is 
attached  quite  differently  since  the  front  end  "A"  is  free  to  move  in 
a  shackle  "B"  bolted  to  the  frame.  A  saddle  "E"  is  clipped  about 
the  spring  at  or  near  its  center  and  is  pivoted  on  the  pin  "F"  attached 
to  the  frame.  The  rear  end  "G"  is  fastened  to  the  axle  "H"  by  a 
shackle  allowing  free  movement  of  the  spring  or  it  may  be  attached 
rigidly  at  this  point.  The  action  of  this  spring  is  similar  to  a  spring- 
board and  when  running  over  rough  roads  permits  the  axle  "H" 
to  oscillate  up  and  down. 

AXLES 

The  springs  are  attached  to  the  axles  which  support  the  weight 
of  the  car.  There  are  two  types  of  axle  construction,  the  dead  axle 
which  remains  stationary  and  the  live  axle  which  revolves  driving 
the  wheels. 

Dead  axles  are  used  for  front  axles  on  two- wheel  drive  machines  and 
for  rear  axles  when  the  final  drive  is  by  chain  and  for  front  and  rear 
when  internal  gear  drive  to  the  wheels  is  used  as  on  the  Nash  Trucks. 


Spring  Pad 


Drag  Link  Ar 


TOP  VIEW 


.Tie  Bar 


Wheel  Hub 


Steering:  Arm 

"If 


.Steering:  Knuckle 

tteel  Forging1         •**• 

SIDE  VIEW 


teering  Knuckle 


Wheel  Hub  \\  Steering  Arm  Spring  Seat 


•  Steel  Tube 
Tie  Bar 


.Steering  Knuckle  Spring  Seat 

Spring  Seat  Axle 

/      ^ 5n 


Fig.  246 — Front  Axles 


274 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


Fig.  246  shows  typical  front  axles.  Dead  axles  may  be  tubular 
(B)  or  "I  beam"  (A)  section,  the  latter  being  a  very  common  con- 
struction for  front  axles.  "I  beam"  axles  are  generally  drop-forged 
from  a  single  piece  of  steel,  spring  seats  being  an  integral  part  as 
shown. 

Live  axles  are  always  split  into  two  parts  each  of  which  is  driven 
by  one  of  the  differential  gears.  A  housing  completely  encloses  axles 
and  gears  protecting  them  from  water,  dust,  and  injury.  There  are 
three  types  of  live  axles;  the  full  floating,  the  three-quarter  floating, 
and  the  semi-floating. 


Fig.  247— Full  Floating  Axle 

Fig.  247  shows  the  construction  of  a  full  floating  live  axle.  The 
wheel  "M"  is  supported  by  two  bearings  "B"  running  directly 
upon  the  axle  housing  "A."  The  axle  shaft  "E"  is  fastened  to  the 
wheel  hub  flange  "N"  by  means  of  the  coupling  "K"  through  which 
the  rotary  motion  of  the  axle  shaft  is  transmitted  to  the  wheel.  The 
axle  shaft  may  be  removed  from  the  housing  without  disturbing  the 
wheel  by  removing  the  coupling  "K." 

The  axle  shaft  "E"  is  not  supported  at  either  end  by  bearings 
and  its  position  is  maintained  by  the  way  it  is  attached  at  both  ends. 


RUNNING  GEAR 


275 


Thus  the  only  strain  on  the  axle  shaft'is  that  of  driving  the  wheels 
and  for  this  reason  it  is  known  as  a  full  floating  axle. 

Fig.  248  shows  a  three-quarter  floating  construction  of  live  axle. 
The  wheel  "M"  is  supported  by  the  single  bearing  "B"  which  runs 
on  the  axle  housing  "A."  The  axle  shaft  "E"  is  rigidly  keyed  to 


Fig.  248— Three-Quarter  Axle 

the  hub  "N"  thus  maintaining  the  alignment  of  the  wheel.  This 
prevents  the  axle  shaft  from  being  removed  without  first  removing 
the  wheel.  As  in  the  full  floating  type  the  axle  shaft  is  not  sup- 
ported by  bearings  at  either  end  but  differs  in  the  type  of  bearings 
employed  and  method  of  attachment  to  the  wheels.  For  this  reason 
it  is  called  a  three-quarter  floating  axle. 

Fig.  249  shows  a  semi-floating  construction  of  live  axle.  The  inner 
end  of  axle  shaft  "D"  is  sometimes  fixed  to  the  differential  gear  or 
else  prevented  from  moving  endwise  by  a  collar  on  the  axle  shaft. 
The  hub  "K"  of  the  wheel  "M"  is  keyed  to  the  outer  end  "H"  of 
the  axle  shaft  as  in  the  three-quarter  floating  type.  The  axle  housing 
"A"  supports  a  bearing  "B"  which  is  placed  inside  its  outer  end. 
Both  the  wheel  and  bearing  "B"  must  be  removed  in  order  to  with- 
draw the  axle  shaft.  This  arrangement  results  in  the  axle  shaft  "E" 
supporting  the  weight  of  the  machine  in  addition  to  transmitting 
rotation  to  the  wheels.  For  this  reason  it  is  called  a  semi-floating  axle. 


276 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


Fig.  249 — Semi-Floating  Axle 


WHEELS 

Wooden  automobile  wheels  are  nearly  always  of  the  artillery 
type,  that  is,  the  spokes  at  the  hub  are  tapered  so  they  wedge  to- 
gether in  a  solid  mass  which  gives  great 
strength.  These  wheels  are  made  of  second 
growth  hickory  and  flanges  are  bolted  to  both 
sides  of  the  wheel  hub  (Fig.  250)  for  reinforce- 
ment. 

The  great  advantage  of  the  wooden  wheel  is 
that  it  has  a  certain  amount  of  natural  spring 
which  absorbs  some  of  the  road  shock.  Wooden 
wheels  are  light  but  strong  and  can  sustain 
heavy  loads.  However,  they  often  break  when 
side  thrust  is  transmitted  to  them  such  as 
occasioned  by  the  machine  skidding  around  a 
corner.  To  make  the  wheels  stronger,  particu- 
larly their  resistance  to  side  thrust,  they  are 
generally  dished.  This  is  accomplished  by 
the  spokes  at  a  slight  angle  with  the 


pi      250 Artillery 

Wood  Wheel          axle  which  results  in  the    plane    of  the  rim 


RUNNING  GEAR 


277 


being  outside  the  plane  of  the  hub.  Greater  resiliency  is  also  obtained 
in  this  way  since  the  road  shocks  are  not  transmitted  radially  to  the 
hub  as  would  be  the  case  with  the  ordinary  construction.  Wooden 
wheels  are  affected  by  dampness  and  must  be  kept  well  painted. 

On  heavy  trucks,  cast  steel  wheels  are  used  in  which  the  spokes, 
hubs,  and  rim  are  all  cast  in  one  piece  their  form  being  very  similar  to 
the  artillery  wood  wheel.  These  wheels  are  very  strong  but  have  the 
objection  of  being  heavier  for  the  additional  strength  obtained. 

Steel  wheels  may  also  be  constructed  without  spokes,  a  solid  disc 
of  metal  joining  the  rim  and  hub.  These  wheels  are  made  of  both 
cast  steel  and  pressed  steel. 

In  order  to  [obtain  light 
weight  without  sacrificing 
strength,  wire  wheels  were 
adopted  of  a  construction  some- 
what similar  to  those  used  on 
bicycles  (Fig.  251).  The  load  is 
not  carried  by  the  spokes  under 
compression  as  in  the  wooden 
wheel,  but  by  those  under  tension, 
all  the  spokes  between  the  hub 
and  the  top  of  the  rim  carrying 
the  load.  These  wheels  are  very 
flexible  and  absorb  a  great  deal 
of  the  road  shock.  Side  'thrust 


Fig.  251— Wire  Wheel 


is  taken  up  in  this  type  of  wheel  by  the  staggard  arrangement  of 
the  spokes. 

BRAKES 

Brakes  and  their  operating  mechanism  are  very  important  parts 
of  a  motor  vehicle.  They  may  be  classified  under  two  general  head- 
ings, the  external  contracting  and  the  internal  expanding.  A  and  B 
(Fig.  252),  show  typical  constructions  of  internal 'expanding  brakes. 
C  and  D  show  typical  constructions  of  external  contracting  brakes. 

In  the  internal  expanding  brake,  shown  at  A,  the  shoes  faced  with 
friction  material  are  hinged  at  a  common  point  as  shown^  their  free 
ends  being  attached  to  a  lever  arm  by  toggle  linkage.  When  the 
lever  is  moved  to  the  left  the  shoes  are  forced  outward  against  the 
brake  drum.  Another  construction  is  shown  at  B  which  employs  a 
cam  to  separate  the  free  ends  of  the  shoes.  In  actual  construction, 
springs  (not  shown)  are  used  to  disengage  the  shoes  when  the  pressure 
on  the  lever  is  released. 


278 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


Fig.  252 — Types  of  Brakes 

In  the  external  contracting  type  shown  at  C,  the  brake  band  lined 
with  friction  material  is  attached  to  a  double  bell  crank  lever  so  that 
when  pulled  to  the  left  the  band  is  contracted  on  the  braked  rum. 
Another  method  of  controlling  the  contraction  of  the  brake  band  is 
shown  at  D.  In  this  construction,  an  adjustment  is  provided  to 
compensate  for  wear  on  the  friction  material.  In  actual  construction, 
springs  are  used  to  hold  the  brake  band  away  from  the  drum  and 
prevent  it  from  dragging  when  released.  The  brake  drums  may  be 
either  attached  to  the  wheels  or  to  the  drive  shaft. 

Fig.  253  shows  a  typical  construction  of  shaft  brake  usecTon  the 
F.  W.  D.  Trucks.  When  a  brake  is  placed  on  the  drive  shaft,  the 
breaking  effect  is  transmitted  equally  to  the  wheels  through  the  power 
transmission  units.  However,  such  a  brake  does  not  overcome  the 
differential  action  and  skidding  may  result. 

When  the  drums  are  on  the  wheels  the  same  drum  is  used  for  both 
external  and  internal  brakes,  the  usual  arrangement  being  to  use  the 
contracting  brake  for  service  and  the  expanding  brake  for  emergency. 
Fig.  254  shows  this  arrangement.  Two  internal  brakes  are  sometimes 
used  eliminating  the  contracting  brake,  because  of  the  protection  from 
ust  and  water  thus  obtained. 


RUNNING  GEAR 


Fig.  253— Shaft  Brake 

Some  method  of  equalizing  the  pull  transmitted  from  the  brake 
pedal  or  lever  to  the  brake  drums  on  the  wheels  is  necessary,  since  an 
unequal  braking  on  the  wheels  will  cause  the  machine  to  skid.  This  is 
accomplished  by  the  use  of  brake  equalizers. 


Fig.  254 — Typical  Wheel  Brake 


280  MOTOR  VEHICLES  AND  THEIR  ENGINES 

Fig.  255  shows  a  typical  arrangement  of  brake  rods  and  equalizers. 
The  foot  pedal  controls  the  external  contracting  brakes  and  the  emer- 
gency lever,  the  internal  expanding  brakes.  When  the  foot  pedal  is 
depressed,  rod  "H"  is  pulled  forward  causing  the  shaft  "X"  to  turn 
pulling  equally  on  the  rods  "L"  and  "K"  which  control  the  brake 
levers  "E."  If  one  brake  is  worn  more  than  another,  the  breaking 
will  not  be  equal  unless  compensated  for  by  adjusting  the  brake  shoes 
or  by  using  a  shorter  rod  between  "X"  and  "E."  The  latter  is  ac- 
complished by  screwing  the  yoke  at  "  E  "  further  up  on  the  rod.  The 
operation  of  the  equalizer  on  the  emergency  brakes  is  identical. 

The  troubles  which  are  usually  experienced  with  brakes  are;  un- 
equal braking,  grabbing  (usually  on  one  brake),  dragging,  and  slipping. 


Fig.  255 — Brake  Rods  and  Equalizers 

To  overcome  unequal  braking,  the  brake  equalizers  may  be  ad- 
justed as  just  explained  or  the  brakes  adjusted  at  the  drum. 

Grabbing  may  be  the  result  of  the  condition 'of  the  friction  sur- 
faces. This  trouble  is  more  apt  to  be  experienced  with  external 
brakes  because  of  their  exposed  position.  It  can  usually  be  over- 
come by  thoroughly  cleaning  and  treating  the  friction  material,  the 
treatment  depending  upon  the  kind  of  material  used.  When  one 
brake  grabs  it  nearly  always  results  from  one  equalizer  rod  being  too 
short  or  the  opposite  rod  being  too  long. 

Dragging  brakes  may  result  from  the  springs  on  the  brakes  not 
completely  disengaging  the  brake  bands  or  shoes  when  released,  but 


RUNNING  GEAR  281 

it  is  more  often  the  result  of  improper  adjustment  of  the  brake  levers. 
In  adjusting  the  equalizers  care  should  be  exercised  not  to  take  up  the 
loose  side,  when  loosening  on  the  tight  side  would  give  the  proper 
movement  of  the  foot  pedal.  It  is  possible  to  shorten  the  equalizer 
rods  so  much  that  the  foot  pedal  or  lever  will  be  in  its  disengaged  posi- 
tion when  the  brakes  are  still  engaged.  The  same  thing  results  when 
the  rods  "R"  or  "H"  (Fig.  256)  are  shortened  too  much.  If  both 
brakes  drag  equally,  the  rods  "R"  or  "H"  should  be  lengthened. 

Slipping  often  results  from  grease  or  oil  getting  on  the  friction 
material.  It  can  be  remedied  by  thoroughly  washing  with  gasoline 
or  kerosene.  Worn  out  brake  linings  will  cause  the  brakes  to  slip  and 
should  be  relined  before  worn  completely  through.  If  the  equalizer 
rods  or  brake  rods  "R"  or  "H"  are  too  long,  slipping  will  result  when 
the  pedal  or  lever  is  applied  since  sufficient  tension  will  not  be  put  on 
the  brake  levers  "D"  or  "P."  The  rods  "H"  and  "R"  should  be 
short  enough  so  that  the  brakes  are  tightened  on  the  drums  before 
the  pedal  is  completely  depressed  or  the  lever  pulled  all  the  way  back. 

Stop  screws  are  sometimes  provided  as  shown  at  "0"  and  "E" 
(Fig.  255)  to  limit  the  motion  of  the  brake  arms.  When  making  ad- 
justments the  setting  of  these  screws  must  be  correspondingly  changed. 

STEERING  GEAR 

In  order  to  change  the  direction  of  motion  of  a  motor  vehicle,  the 
position  of  the  steering  wheels  must  be  altered.  These  are  usually  the 
front  wheels  although  some  machines  are  steered  by  turning  both  the 
front  and  rear  wheels.  In  a  horse-drawn  vehicle  the  front  and  rear 
axles  are  parallel  to  each  other  when  it  is  moving  straight  ahead  and 
and  the  front  and  rear  wheels  are  in  alignment.  When  turning  the 
front  axle  is  swung  out  of  parallel  with  the  rear  axle,  pivoting  at  a 
point  mid-way  between  the  front  wheels.  This  requires  a  movable 
front  axle  with  but  a  single  point  of  support  for  the  front  end  of  the 
vehicle  and  such  a  construction  would  be  impracticable  for  a  motor 
vehicle.  The  great  weight  supported  by  the  front  axle  prohibits  its 
movement  and  an  unstable  condition  would  exist  if  the  front  axle  were 
moved  out  of  parallel  with  the  rear  axle.  In  order  for  the  wheels  to  be 
moved  while  the  axle  is  held  rigid,  each  wheel  is  separately  pivoted  at 
either  end  of  the  axle.  These  pivoted  ends  are  called  the  knuckles 
and  are  connected  by  a  tie  rod  so  that  both  wheels  move  together. 

For  a  wheel  to  follow  a  curved  path  without  slipping  it  must  at 
all  times  be  tangent  to  this  path  and  perpendicular  to  the  radius  of 
curvature.  Fig.  256  shows  the  paths  of  the  front  and  rear  wheels  of 
both  a  horse-drawn  vehicle  and  a  motor  vehicle  when  changing  di- 


282  MOTOR  VEHICLES  AND  THEIR  ENGINES 

rection.  The  front  wheels  of  the  horse-drawn  vehicle  remain  parallel 
at  all  times  since  they  are  perpendicular  to  a  common  radius.  The 
intersection  of  a  line  passing  through  the  front  axle  with  one  passing 
through  the  rear  axle  locates  the  point  about  which  the  vehicle  is 
turning.  In  the  case  of  the  motor  vehicle,  however,  the  front  wheels 
are  not  parallel  when  changing  direction,  since  they  are  perpendicular 
to  two  different  radii  which  both  intersect  a  line  passing  through  the 
rear  axle  at  the  point  about  which  the  vehicle  is  turning.  The  front 
wheels  in  this  case  are  parallel  with  each  other  only  when  the  steering 
knuckle  spindles  are  in  line  with  the  stationary  axle  which  will  be 
when  the  vehicle  is  moving  straight  ahead. 


Fig.  256 — Steering  Arrangements  Compared 

If  the  steering  knuckle  arms  projected  at  right  angles  to  the  axle, 
the  tie  rod  would  cause  both  wheels  to  move  through  the  same  angle 
and  be  parallel  at  all  times.  This  is  prevented  by  inclining  the 
knuckle  arms  toward  each  other  so  that  their  center  lines  intersect  at 
the  center  of  the  rear  axle.  In  this  way  the  inside  wheel  will  be 
turned  more  than  the  outside  one  when  changing  direction. 

Fig.  257  shows  a  conventional  arrangement  of  the  parts  composing 
the  steering  apparatus.  The  steering  wheel  "K"  is  fixed  to  the  post 
"H"  which  is  generally  encased.  The  gear  "G"  is  attached  to  the 
post  "H"  and  meshes  with  the  gear  "L"  which  is  keyed  to  a  short 
1  shaft  the  other  end  of  which  is  square  and  carries  a  lever  or  pitman 
arm  "F."  The  arm  "F"  is  connected  by  a  drag  link  "E"  to  one  of 
the  arms  "C"  of  the  steering  knuckle  "B."  The  two  steering 
knuckle  arms  "C"  are  connected  by  the  tie  rod  "D"  transmitting 
the  turning  motion  to  both  knuckles.  Each  knuckle  is  pivoted  on  a 
king  bolt  which  holds  it  in  place  on  the  axle  forming  a  bearing  about 
which  it  turns.  The  wheels  are  carried  by  the  steering  knuekle 
spindles  "R"  forged  integral  with  the  knuckle. 


RUNNING  GEAR 


283 


To  make  steering  easier,  both  the  plane  of  the  wheel  and  the  axis 
about  which  the  steering  knuckle  turns  are  inclined  toward  each 


Fig.  257 — Steering  Apparatus 


other.  This  is  called  CAMBER  (Fig.  258) .  If  a  line  passing  through 
the  axis  of  the  king  bolt  strikes  the  ground  at  the  point  where  the 
wheel  rests,  the  wheel  is  pivoted  so  as  to  turn  about  its  point  of  con- 
tact with  the  ground  and  consequently  turns  easily.  However,  the 
amount  of  inclination  is  never 
this  great,  usually  being  just 
enough  to  make  the  spokes  of 
dished  wheels  vertical.  Hence 
this  pivot  point  generally  falls 
outside  the  wheel's  point  of 
contact  with  the  ground .  CAST- 
ER EFFECT  is  obtained  by 
canting  the  axle  so  that  the 
bottom  of  the  king  bolt  is  ap- 
proximately Y%  of  an  inch  ahead 
of  the  top  where  the  car  is  level. 
This  tends  to  keep  the  steering 
wheels  straight  in  the  direction 
the  machine  is  traveling.  The  resistance  of  the  road  to  the  motion 
of  the  machine  tends  to  spread  the  front  edges  of  the  wheels  apart. 
For  this  reason  the  front  wheels  are  GATHERED  slightly  the 
distance  between  the  front  edges  being  somewhat  less  than  that  be- 
tween their  rear  edges. 


Fig.  258— Camber 


284 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


There  are  two  types  of  steering  gear,  the  reversible  and  the  ir- 
reversible. The  former  transmits  road  shocks  back  through  the 
steering  gear  causing  the  steering  wheel  to  turn.  The  latter  will  not 
transmit  road  shocks  through  the  steering  gear,  the  steering  wheel 
remaining  steady.  The  type  of  steering  apparatus  will  depend  upon 
whether  or  not  the  gear  keyed  to  the  steering  arm  can  turn  the  gear 
keyed  to  the  steering  post;  and  when  worm  gears  of  proper  pitch  are 
used  this  is  not  possible,  an  irreversible  gear  resulting.  A  reversible 
gear  results  when  bevel  gears  are  used  while  the  nut  and  screw  con- 
struction may  be  either  reversible  or  irreversible,  depending  upon  the 
pitch  of  the  screw. 

To  absorb  the  road  shock  especially  when  the  irreversible  type  of 
steering  gear  is  used,  the  ends  of  the  drag  link  are  enlarged  and  carry  a 
spring  thrust  device.  Within  certain  limits,  movements  of  the  steer- 
ing wheel  will  cause  compression  of  these  springs  preventing  undue 
pressures  being  exerted  on  the  steering  knuckle  arms  or  the  pitman 
arm.  The  tension  on  these  springs  is  adj ustable  and  they  are  generally 
packed  with  grease  and  enclosed  in  a  leather  boot. 


Fig.  259 — Irreversible  Sleering  Gear 

Fig.  259  shows  a  typical  irreversible  steering  gear  which  is  em- 
ployed on  the  Dodge  Car. 

BEARINGS 

A  bearing  is  necessary  when  one  moving  part  of  a  machine  turns 
on  another.     Energy  is  required  to  overcome  the  friction  between 


RUNNING  GEAR 


285 


moving  surfaces  in  contact  and  depends  upon  the  total  area  and  the 
materials  composing  these  surfaces.  In  the  motor  propelled  vehicle 
it  is  important  that  the  power  generated  by  the  engine  should  be 
delivered  to  the  traction  members  with  as  little  loss  as  possible.  For 
this  reason  all  engine  bearings  and  those  used  in  the  various  units  of 
the  power  transmission  system  are  designed  to  reduce  the  frictional 
loss  to  a  minimum.  There  are  three  kinds  of  bearings  in  common  use; 
plain,  roller,  and  ball. 

Plain  bearings  are  almost  universally  used  throughout  the  engine 
though  they  consume  considerably  more  energy  than  the  other  types. 
However,  they  are  necessary  in  order  to  obtain  sufficient  bearing 
surface  to  carry  the  heavy  thrust  resulting  from  the  power  impulses  in 
the  cylinders.  The  usual  construction  is  to  finish  and  polish  the  shaft 
or  pin  to  a  mirror-like  surface*,  the  surface  against  which  it  bears 
being  of  babbit  or  other  low  friction  metal.  Since  there  is  considerable 
friction  surface  very  good  lubrication  is  necessary  and  special  pro- 
visions such  as  oil  grooves  must  be  made  to  obtain  the  best  lubrica- 
tion possible.  Plain  bearings  are  also  found  on  all  parts  of  the 
machine  where  a  loss  of  energy  due  to  friction  does  not  make  any 
difference,  such  as  on  brake  pedals,  gear  shift  levers,  spring  bolts,  etc. 

Roller  and  ball  bearings  are  used  throughout  the  power  transmis- 
sion system,  the  former  being  used  when  the  load  is  heavy  or  the  end 
thrust  is  great  and  the  latter  where  the  load  on  the  bearing  is  uniform 
and  not  heavy. 


\Coi7f. 


Fig.  260 — Anti-Friction  Bearings 

Fig.  260  shows  some  commercial  construction  of  ball  and  roller 
bearings.  The  ball  bearing  at  A  is  a  cup  and  cone  design.  This 
bearing  has  an  angular  contact  and  is  capable  of  taking  radial  and 
light  thrust  loads.  Such  bearings  are  adjustable  to  a  slight  degree, 


286  MOTOR  VEHICLES  AND  THEIR  ENGINES 

as  lost  motion  may  be  eliminated  by  forcing  the  cup  or  cone  into  more 
intimate  contact  with  the  balls.  The  ball  bearing  shown  at  B  is  of  the 
annular  type  and  is  adapted  only  for  radial  loads  and  very  light  end 
thrust  and  is  not  adjustable.  Since  there  is  only  a  point  contact  in 
ball  bearings,  friction  is  a  minimum  requiring  light  oil  and  infrequent 
lubrication. 

The  roller  bearing  shown  at  C  is  provided  with  straight  rollers  and 
can  take  only  radial  loads.  That  shown  at  D  employs  tapered  race 
members  and  correspondingly  tapered  rollers.  Bearings  of  this  type 
will  carry  not  only  radial  loads  but  also  resist  end  thrust.  This  bear- 
ing is  adjustable  for  wear  by  moving  one  of  the  race  members  into 
closer  contact  with  the  rollers.  Roller  bearings,  having  a  line  con- 
tact, are  stronger  than  ball  bearings  but  absorb  more  power  because 
of  the  increased  surfaces  in  con- 
tact. Therefore  heavier  oil 
and  more  lubrication  is  neces- 
sary than  with  ball  bearings. 

Fig.  261  shows  a  typical 
installation  of  conical  roller 
bearings  on  the  front  wheels 
and  knuckles  of  a  modern 
automobile.  With  this  arrange- 
ment both  the  radial  and  Fig.  261 — Roller-Bearing  Installation 
thrust  loads  are  carried. 

Roller  bearings  are  either  solid  or  constructed  as  shown  in  Fig.  263. 
These  rollers  are  constructed  by  rolling  strips  of  steel  into  helices  and 
are  arranged  in  the  bearing  so  that  right  and  left  helices  alternate. 
This  type  gives  increased  flexibility  reducing  the  transmitted  strain 
resulting  from  sudden  shock.  In  addition  the  arrangement  of  the 
helices  is  such  as  to  keep  the  lubricant  in  continuous  circulation  over 
the  entire  bearing  surface. 

To  space  the  balls  or  rollers  in  a  bearing,  cages  or  separators  are 
used  and  are  so  constructed  as  to  present  the  minimum  amount  of 
surface  to  the  moving  parts.  These  cages  are  usually  made  as  light 
as  possible  and  of  soft  material,  such  as  brass. 

MUFFLERS 

Mufflers  are  used  on  motor  vehicles  to  reduce  the  noise  of  the  es- 
caping exhaust  gases.  This  noise  results  from  the  sudden  expansion 
of  the  gases  when  the  exhaust  valves  are  opened.  It  is  not  difficult  to 
muffle  the  gases  so  that  there  will  be  but  little  noise,  yet  it  is  quite  a 
problem  to  do  it  without  producing  back  pressure  in  the  muffling 


RUNNING  GEAR 


287 


Jnlct 


Inlet 


I       »      »       »       »       » 


Fig.  262 — Typical  Mufflers 


288 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


device  that  will  cause  considerable  loss  of  power.  A  muffler  should 
offer  minimum  resistance  to  the  passage  of  the  gas  and  means  should 
be  provided  for  not  only  breaking  the  entering  stream  into  smaller 
streams  but  the  capacity  of  the  muffler  should  be  sufficiently  large  to 


STEEL  SLEEVE 


Fig.  263— Hyatt  Bearings 

permit  the  gases  to  expand  to  nearly  atmospheric  pressure  before  they 
are  discharged  into  the  ay\  As  the  gas  is  delayed  in  its  passage  through 
the  muffler  from  the  cylinders  to  the  open  air  its  temperature  is 
reduced,  thus  decreasing  its  expansion.  Fig.  262  shows  several  com- 
mercial designs  of  mufflers,  all  built  on  the  same  principle,  but  dif- 
fering somewhat  in  construction. 


CHAPTER  XXVII 


TIRES  AND  RIMS 

The  wheels  of  motor  vehicles  are  almost  without  exception  pro- 
vided with  rubber  tires.  If  the  wheels  were  not  properly  tired  the 
vibration  transmitted  to  the  machinery  would  soon  cause  it  to  shake 
itself  to  pieces.  The  great  weight  and  speed  of  motor  vehicles  and 
the  delicate  construction  of  their  machinery  require  additional 
protection  to  that  afforded  by  the  springs  alone. 

There  are  two  types  of  tires  in  general  use  at  the  present  time. 
These  are  the  solid  tire  and  the  pneumatic  tire.  The  former  consists 
of  a  solid  band  of  rubber,  the  resiliency  or  spring  of  the  material  itself 
being  depended  upon  to  absorb  the  road  shock.  This  type  of  tire 
is  used  on  trucks  and  other  heavy  motor  vehicles  where  the  speed  is 
comparatively  low.  On  lighter  cars  of  higher  speed  solid  tires  would 
not  be  suitable  since  they  would  not  absorb  sufficient  vibration.  For 
this  reason  pneumatic  tires  are  used.  With  the  pneumatic  tire  not 
only  the  resiliency  of  the  rubber  but  also  that  of  the  air  with  which  it 
is  inflated  absorbs  road  shocks  which  would  otherwise  be  transmitted 
to  the  machine.  This  is  because  a  pneumatic  tire  is  compressed 
when  it  strikes  an  obstacle  in  the  road  while  a  solid  tire  is  only 
distorted. 

The  pneumatic  tire  in  general  use  is  of  the  double  tube  construc- 
tion, being  composed  of  two  members,  the  inner  tube  and  the  shoe 
or  casing.  The  inner  tube  is  utilized  to  retain  the  air  and  is  made  of 
pure  Para  rubber  approximately  one-sixteenth  of  an  inch  in  thickness. 
Such  a  tube  would  not  be  sufficiently  strong  to  run  directly  on  the 
road  surface,  necessitating  the  use  of  an  outside  casing  of  sufficient 
strength  and  wearing  qualities  to  protect  the  inner  tube.  The  casing 
is  provided  with  some  means  of  attachment  to  the  rim  so  that  when 
an  inner  tube  is  placed  in  it  and  inflated  the  casing  will  be  held 
firmly  in  place. 

Fig.  264  shows  a  cross-section  of  a  pneumatic  tire.  The  main 
portion  of  the  outer  casing  is  composed  of  alternate  layers  of  Sea 
Island  cotton  fabric  and  high-grade  rubber  composition.  This 
composition  is  forced  into  the  meshes  of  the  cloth  so  that  when 
vulcanized  all  the  layers  of  fabric  will  be  intimately  joined  together. 
The  fabric  body  is  the  part  of  the  casing  that  gives  it  its  strength, 
the  number  of  layers  of  fabric  used  depending  upon  the  size  of  the 
tire.  Outside  of  the  fabric  body  is  placed  a  layer  of  very  resilient 

289 


290 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


Bead 


Breaker  Strips 


abricBodj 


Km  Channel 


Fig.  264 — Cross-Section  of  Pneumatic  Tire 

Para  rubber  called  the  padding,  which  is  thickest  at  the  center  of 
the  tread  and  tapers  off  on  either  side  as  shown.  The  purpose  of  the 
padding  is  to  give  a  certain  amount  of  elasticity  to  the  casing.  On 
top  of  the  padding  and  extending  slightly  beyond  the  center  of  the 
tread  are  placed  several  pieces  of  heavy  fabric  called  breaker  strips 
which  offer  resistance  to  any  sharp  object  which  penetrates  the  tread, 
tending  to  deflect  it  to  one  side,  thus  protecting  the  padding  and 
fabric  body.  The  outside  surface  is  called  the  tread  and  is  that  part 
of  the  tire  which  is  subjected  to  the  greatest  wear  since  it  is  in  con- 
tact with  the  road  surface.  It  must  resist  the  abrasive  action  of  the 
road  and  when  used  on  driving  wheels  it  suffers  additional  wear  due 
to  the  tractive  effort  producing  friction  between  the  wheels  and  the 
ground.  For  this  reason  the  tread  must  be  of  very  tough  rubber 
composition  and  differs  from  the  material  used  for  the  padding  and 
inner  tube  in  not  possessing  so  great  a  degree  of  elasticity.  This 
is  sacrificed  in  favor  of  great  strength  and  resistance  to  wear  which, 
of  course,  is  essential. 

|There  are  two  processes  of  building  tires  used  by  modern  tire 
manufacturers.   The  first  of  these  is  known  as  the  "  moulded  process  " 


TIRES  AND  RIMS  291 

where  the  tire  is  built  up  on  a  core  and  then  clamped  in  a  mould  and 
vulcanized  by  steam.  The  other  is  known  as  the  "  wrapped  tread 
process  "  where  the  tire  is  built  up  on  a  core  as  before  and  then  tightly 
wrapped  with  strips  of  canvas  and  vulcanized. 

Another  construction  of  pneumatic  tire  is  the  cord  tire.  It  does 
not  differ  materially  in  the  way  in  which  it  is  built  up  and  vulcanized, 
but  instead  of  layers  of  fabric  being  used  the  fabric  body  is  composed 
of  layers  of  cord,  rubber  composition  being  used  as  before.  When 
the  tire  is  vulcanized  the  layers  of  cord  become  filled  with  rubber  and 
the  whole  mass  is  bound  firmly  together.  Owing  to  its  construction 
the  cord  tire  cannot  be  as  easily  repaired  as  the  fabric  tire  and  it 
requires  expert  workmanship  to  repair  a  portion  of  a  cord  tire  injured 
by  a  blow-out.  Tires  of  this  construction  are  much  more  resilient 
and  give  greater  mileage  than  the  stiffer  fabric  tire  making  them 
more  desirable.  There  is  also  a  cord-fabric  tire  in  which  the  layers 
of  cord  composing  the  fabric  body  are  replaced  by  layers  of  fine  cord 
woven  into  a  fabric.  These  tires  are  almost  as  flexible  as  the  original 
cord  tire  but  are  much  easier  to  repair. 


Regular  Clincher  Type         A  Straight  Side  Type 


Fig.  265— Types  of  Casings 

Two  types  of  casings  are  supplied  differing  in  their  method  of 
attachment  to  the  rim.  They  are  the  clincher  and  the  straight  side 
or  Dunlop  types.  At  A  (Fig.  265)  is  shown  a  clincher  casing.  The 
fabric  is  looped  about  a  triangular  insert  of  leather  running  along  the 
edges  of  the  tire  and  forming  a  bead.  It  is  this  bead  which  grips  the 
flanges  of  the  rim  when  the  tire  is  inflated.  This  bead  is  either  hard 
or  soft,  depending  upon  whether  the  tire  is  to  be  used  on  Q.  D.  or 
straight  clincher  rims.  At  B  (Fig.  265)  is  shown  a  straight  side  cas- 
ing. No  bead  is  provided  in  this  case  the  fabric  being  looped  about 
strands  of  piano  wire  running  around  the  inner  edges  of  the  tire. 
Since  the  steel  wire  does  not  stretch  the  tire  will  be  held  snugly 
against  the  rim  when  inflated,  the  rim  flanges  preventing  it  from 
slipping  off  the  rim  sideways. 


292 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


Inner  tubes  are  made  from  seamless  rubber  tubing  of  uniform 
thickness  the  most  resilient  rubber  obtainable  being  used.  The 
tubing  is  cut  the  right  length  (which  depends  upon  the  diameter  of 
the  wheel)  and  the  two  ends  are  permanently  joined  by  vulcanizing 
them  together.  Motor-cycle  tubes  are  often  made  with  two  ends 
separately  vulcanized  in  order  to  facilitate  their  removal  from  the 
casing.  The  only  opening  into  the  tube  is  where  the  valve  stem  is 
inserted  which  is  an  air-tight  joint. 


Fig.  266— Valve 

Air  is  introduced  into  the  inner  tube  through  a  simple  automatic 
valve  (Fig.  266).  The  valve  proper  is  held  against  its  seat  by  a 
light  spring  and  will  only  open  when  the  valve  stem  is  depressed 
by  hand  or  when  air  pressure  is  forced  against  it  in  inflating  the 
tire.  When  inflating  a  tire  the  air  pressure  on  the  inside  holds  the 
valve  firmly  in  place  whenever  the  incoming  pressure  is  stopped. 
The  valve  must  be  screwed  in  tight  enough  to  compress  the  rubber 
packing  and  make  it  swell  out  against  the  walls  of  the  valve  tube, 
forming  an  air-tight  joint.  The  lower  end  of  the  valve  tube  or 
stem  is  inserted  in  the  inner  tube,  a  tight  joint  being  obtained  by 
screwing  down  a  nut  on  the  rubber  tube  and  locking  it  in  place, 
the  joint  being  vulcanized  and  protected  by  a  spring  clamp. 

The  tread  of  the  tire  may  be  smooth  or  non-skid.  The  smooth 
tread  has  the  disadvantage  of  poor  traction  and  liability  of  skidding 
on  muddy  roads  which  has  led  to  the  development  of  the  so-called 
non-skid  tread.  Non-skid  or  rough  treads  give  better  traction,  wear 
longer,  and  to  some  extent  prevent  skidding. 


TIRES  AND  RIMS 


293 


Fig.  267  shows  several  examples  of  commercial  non-skid  treads. 
It  is  customary  to  equip  passenger  cars  with  non-skid  treads  on  the 
rear  wheels  and  plain  treads  on  the  front  wheels. 


ft 


Fig.  267— Some  Non-Skid  Treads 

The  best  preventive  against  skidding  is  the  use  of  chains.  Tire 
chains  are  made  up  of  a  series  of  short  cross  chains  attached  to  two 
long  chains,  the  ends  of  which  are  snapped  together  on  the  inside  and 
outside  of  the  wheels.  Fig.  268  shows  the  method  of  applying  non- 


Fig.  268 — How  Chains  Are  Applied 

skid  chains.  Chains  increase  the  traction  and  reduce  skidding  to  a 
minimum.  They  should  be  applied  both  to  the  front  and  rear  wheels 
to  obtain  the  best  results  and  should  be  supplied  for  use  with  both 
solid  and  pneumatic  tires.  Chains  should  be  applied  only  when  it  is 
necessary  to  travel  over  roads  that  are  very  soft  and  muddy  and 
should  be  immediately  removed  when  hard  road  surfaces  are  again 


294  MOTOR  VEHICLES  AND  THEIR  ENGINES 

encountered.    This  is  because  the  cross  chains  chafe  the  tires,  causing 
bruising  of  the  tread  and  excessive  wear. 

There  are  two  types  of  rims  for  pneumatic  tires,  the  clincher  arid 
the  straight  side  or  Dunlop.  The  clincher  rim  may  be  plain  one- 
piece,  quick  detachable,  or  demountable.  The  plain  clincher  rim 
is  very  little  used  except  on  light  cars,  a  typical  construction  being 
shown  in  Fig.  264.  The  straight  side  rim  may  be  quick  detachable 
or  demountable,  the  quick  detachable  type  usually  being  convertible 
permitting  either  clincher  or  straight  side  tires  to  be  used. 


Fig.  269— Rim  Forms 

Fig.  269  shows  a  quick  detachable  rim  with  the  clincher  rim  re- 
versed to  take  both  types  of  tires.  To  remove  the  tire  from  a  quick 
detachable  rim  it  is  only  necessary  to  deflate  it  and  press  in  the  clincher 
ring,  disengaging  the  locking  ring,  which  is  lifted  out  allowing  the 
clincher  ring  to  be  removed.  This  permits  one  whole  side  of  the  tire 
to  be  pulled  off  the  rim  giving  a  quick  and  easy  access  to  the  inner 
tube  for  replacement  or  repair. 

Numerous  forms  of  demountable  rims  have  been  devised  all  of 
which  are  constructed  along  practically  the  same  lines.  The  rim 
is  held  in  place  by  a  series  of  lugs  or  wedges  which  are  bolted  to  the 
felloe  of  the  wheel.  By  taking  off  the  nuts  holding  these  in  place 
the  whole  rim  may  be  slipped  off  the  wheel  and  another  substituted. 
The  advantage  of  the  demountable  rim  is  that  an  entire  spare  casing, 
inner  tube,  and  rim  may  be  carried  inflated  and  ready  for  use.  In 
case  of  tire  trouble  on  the  road,  tires  can  be  quickly  changed  and  the 
necessary  tire  repairs  made  at  the  end  of  the  trip. 

Demountable  rims  may  be  either  quick  detachable  or  of  split 
construction.  The  former  permits  the  removal  of  the  casing  without 
taking  the  rim  off  the  wheel  while  with  the  latter  type  it  is  necessary 
to  remove  the  rim  before  the  casing  can  be  detached. 


TIRES  AND  RIMS 


295 


Locking 
Wedge 


ILoc£in$BoJt      Felloe 


Fig.  270 — Demountable  Rim 

Fig.  270  shows  a  quick  detachable  demountable  rim  for  clincher 
tires.  The  locking  wedge  is  held  in  place  by  lugs  bolted  to  the  felloe 
of  the  wheel.  When  the  retaining  lugs  are  removed  the  rim  may  be 
pulled  from  the  wheel,  the  side  where  the  valve  stem  goes  through 
the  felloe  being  lifted  off  last. 

On  trucks  and  other  heavy  motor  vehicles,  pneumatic  tires  are  not 
generally  used  because  of  the  large  size  that  would  be  required  to 
carry  the  load.  Since  their  speed  as  a  rule  is  limited,  solid  rubber 
tires  may  be  employed  to  advantage.  These  are  moulded  from  some 
special  rubber  composition  in  one  continuous  ring  and  are  usually 
provided  with  some  form  of  re-enforcement  at  their  base  where  they 
are  clamped  into  the  rim.  Modern  truck  tires  are  quick  detachable 
or  demountable  and  are  usually  held  in  place  with  wedges  or  flanges 


Fig.  271— Solid  Tire 

of  similar  construction  to  those  used  on  pneumatic  rims.  Fig.  271 
shows  a  typical  solid  rubber  tire  on  a  demountable  rim.  It  is  re- 
enforced  by  a  hard  rubber  base  and  clamped  into  place  in  its  rim. 


296  MOTOR  VEHICLES  AND  THEIR  ENGINES 

When  the  load  on  the  rear  wheels  is  particularly  heavy,  extra  wide 
tires  or  dual  tires  are  employed.  Their  construction  does  not  differ 
materially  from  the  single  tire  type  the  same  method  of  attachment 
being  employed  but  they  are  not  so  apt  to  slip  side-ways  on  slippery 


When  inserting  an  inner  tube  in  a  casing,  care  must  be  taken  not  to 
pinch  or  twist  it  and  to  pull  the  valve  stem  through  the  rim  straight. 
The  following  is  the  procedure  when  applying  a  casing  to  a  demounta- 
ble, rim.  Clean  out  the  casing  and  be  sure  it  is  dry.  Shake  some 
powdered  mica  or  soapstone  into  the  casing  and  turn  it  once  or  twice 
around  to  insure  its  whole  interior  being  coated  and  then  remove  what 
remains.  Insert  the  inner  tube  and  apply  the  casing  to  the  rim,  put- 
ting the  valve  stem  through  the  hole  in  the  rim  first.  Assemble  the  rim 
and  inflate  the  tire  to  about  twenty  pounds  pressure.  Then  bounce 
the  tire  up  and  down  turning  it  through  two  or  three  revolutions 
which  permits  the  inner  tube  to  straighten  out  and  assume  its  natural 
position,  preventing  pinching  or  twisting  of  the  tube  or  the  valve 
stem  being  crooked.  Finish  .inflating  the  tire  to  the  proper  pressure 
for  its  particular  size. 

The  following  table  gives  the  proper  pressures  to  which  different 
sized  tires  should  be  inflated  as  recommended  by  leading  tire  manu- 
facturers: 

Diameter  of  Tire  Air  Pressure  in  Tire 

Inches  Pounds  per  Square  Inch 

2J  50 

3  60 
3J  70 

4  80 
4|  90 

5  90 
5J  95 

6  100 

The  air  pressure  in  a  tire  increases  when  the  machine  is  driven 
due  to  the  heat  set  up  by  the  friction  of  traction.  This  must  be  taken 
into  consideration  when  pumping  up  a  tire  before  running.  It  is  ad- 
visable especially  on  a  warm  day  to  release  some  of  the  pressure  after 
running  some  distance.  The  pressure  should  first  be  tested  and  for 
this  purpose  a  tire  pressure  gauge  should  be  provided  as  part  of  the 
equipment  of  every  machine  having  pneumatic  tires. 

The  life  of  the  tire  depends  directly  upon  the  amount  of  care  and 
attention  that  it  receives.  Probably  no  part  of  the  machine  is  less 
looked  after  than  the  tires  which  are  generally  never  given  a  thought 
until  tire  trouble  results. 


TIRES  AND  RIMS  297 

When  returning  from  a  run  a  careful  inspection  of  the  tires  should 
be  made  and  all  cuts  and  holes  should  be  immediately  cleaned  out 
and  vulcanized.  If  there  is  any  oil  or  grease  on  the  tires  it  should  be 
cleaned  off,  since  oil  attacks  the  rubber  causing  it  to  deteriorate. 
Inflate  all  tires  fully.  The  dead  weight  of  the  machine  should  never 
be  allowed  to  rest  on  a  deflated  tire.  Before  starting  out  upon  a  run 
the  pressure  in  the  tires  should  be  tested  and  any  tires  not  pumped 
up  to  the  required  pressure  should  be  inflated.  Running  on  tires 
which  are  not  properly  inflated,  causes  them  to  be  distorted,  the 
amount  of  distortion  depending  upon  the  pressure  in  the  tire.  Such 
distortion,  no  matter  how  small,  causes  the  layers  of  the  fabric  to  be- 
come separated  from  each  other  and  from  the  tread  surface  resulting 
in  the  tire  soon  going  to  pieces.  If  the  pressure  is  allowed  to  become 
so  low  that  the  tires  spread  out  flat  on  the  road,  rim  cutting  may  re- 
sult and  the  inner  tube  will  probably  be  ruined. 

Fast  driving  and  sudden  starting  or  stopping  of  the  machine  is 
very  hard  on  tires  causing  the  tread  surface  to  be  worn  where  the 
wheels  slide  on  the  ground.  When  a  machine  turns  a  corner  it  tends 
to  slide  outward  and  if  the  speed  is  great  enough  the  tread  surface  of 
the  tires  will  be  injured.  Running  in  street  car  tracks  or  in  deep 
ruts  chafes  the  sides  of  the  tires  and  must  not  be  indulged  in. 

It  is  very  important  to  have  the  front  and  rear  wheels  in  alignment. 
If  out  of  line  the  tire  treads  will  wear  in  a  very  short  time,  a  difference 
of  less  than  an  inch  causing  a  grinding  wear  on  the  tires  especially  the 
front  ones. 

The  same  size  tires  must  be  used  on  both  pairs  of  wheels  in  order 
to  equalize  the  traction.  A  plain  tread  tire  should  never  be  used  on 
one  rear  wheel  when  a  non-skid  tire  is  on  the  other.  In  addition  to 
excessive  wear  on  the  tires  this  also  causes  the  differential  gears  to  be 
unduly  worn. 

Inner  tubes  should  be  kept  in  a  cool  dry  place  away  from  oil, 
gasoline,  and  tools.  It  is  best  to  keep  them  in  a  bag  well  dusted  with 
soapstone.  Spare  casings  should  not  be  exposed  to  the  rays  of  the 
sun.  When  a  spare  tire  is  carried  inflated  it  should  be  encased  in  a 
tire  cover. 

TIRE  TROUBLES 

Probably  the  most  common  tire  trouble  on  the  road  is  puncture. 
When  a  tire  is  punctured  not  only  the  hole  through  the  inner  tube  but 
also  that  through  the  casing  should  be  repaired.  The  former  may  be 
patched  or  better  still  vulcanized  while  the  opening  through  the  casing 
may  be  filled  with  ''tire  dough "  temporarily  and  later  permanently 
vulcanized. 


298  MOTOR  VEHICLES  AND  THEIR  ENGINES 

Blow-out  is  the  most  serious  tire  trouble  that  will  be  encountered 
and  can  only  be  repaired  temporarily  on  the  road.  If  an  extra  tire  is 
not  carried,  repair  the  injured  casing  by  inserting  a  new  inner  tube 
and  using  an  inside  and  outside  boot  to  strengthen  the  point  in  the 
casing  where  the  blow-out  occurred. 

Small  or  thin  cuts  are  often  overlooked  but  should  be  immediately 
vulcanized  when  noticed.  This  is  equally  important  when  solid  tires 
are  used.  A  stone  bruise  is  caused  by  running  over  the  corner  of  a 
brick  or  other  hard  object  which  tears  part  of  the  tread  surface  from 
the  tire.  The  loose  rubber  should  be  trimmed  away  and  the  hole 
filled  up  and  vulcanized. 

Sand  blisters  are  caused  by  sand  or  grit  from  the  road  working 
in  through  overlooked  punctures  or  cuts  in  the  casing  and  collecting 
between  the  tread  and  fabric  body.  They  should  be  opened  by 
cutting  in  with  a  sharp  knife  and  the  accumulated  dirt  thoroughly 
cleaned  out  with  gasoline.  The  opening  should  then  be  filled  and 
vulcanized. 

For  making  road  repairs  a  tire  repair  kit  should  be  carried  con- 
taining cement,  patches,  tape,  un vulcanized  rubber,  extra  parts,  etc., 
and  the  necessary  tools.  A  small  gasoline  torch  vulcanizer  is  a  very 
valuable  addition  and  all  repairing  of  inner  tubes  should  be  done  by 
vulcanizing  rather  than  by  using  patches. 


CHAPTER  XXVIII 


HOW  TO  DRIVE 

Before  starting  an  engine  the  driver  should  see  that  the  gear  shift 
lever  is  in  neutral  position  and  that  the  emergency  brakes  are  set. 
The  spark  lever  should  be  set  at  the  proper  position.  If  battery 
ignition  is  used  it  is  best  to  have  the  lever  in  full  retard  position,  as 
the  spark  will  occur  no  matter  how  slow  the  engine  is  cranked.  If 
magneto  ignition  is  used  the  lever  should  be  advanced  slightly  as 
a  hotter  spark  is  obtained  in  the  advanced  position  than  in  the 
retarded.  There  is  less  probability  of  a  kick  back  when  starting  on 
magneto  since  it  is  necessary  to  turn  the  engine  at  a  fairly  high  speed, 
approximately  100  R.  P.  M.,  to  generate  sufficient  current  to  produce 
a  spark. 

The  position  of  the  throttle  hand  control  should  be  set  so  that  the 
throttle-  will  be  slightly  open.  In  case  the  carburetor  is  equipped 
with  an  air-choking  device  this  should  be  closed  to  cause  a  rich 
mixture  for  starting. 

The  ignition  switch  should  be  turned  on  and  the  engine  cranked 
by  pulling  up  quickly  on  the  crank  handle  a  quarter  turn  at  a  time. 
If  an  electric  cranking  motor  is  provided  depress  the  starting  button 
and  advance  the  spark.  If  magneto  ignition  is  used  it  is  best  to  spin 
the  engine.  Crank  the  engine  with  the  left  hand  if  possible  and 
stand  in  such  a  position  that  if  the  engine  should  kick  back  the 
crank  will  not  cause  injury. 

After  the  engine  has  started  release  the  choke  on  the  carburetor, 
advance  the  spark,  and  close  the  throttle  to  a  position  which  will 
prevent  racing.  If  a  special  dash  adjustment  is  provided  for  regu- 
lating the  mixture  allow  this  to  remain  in  a  position  to  cause  a  rich 
mixture  until  the  engine  warms  up. 

TO  START  THE  CAR 

Allow  the  engine  to  warm  up  sufficiently  to  overcome  missing 
and  to  run  smoothly.  When  satisfied  that  the  engine  is  running 
properly  release  the  emergency  brake.  In  case  the  car  is  on  a  grade 
apply  the  foot  brake  to  prevent  the  car  from  moving.  Press  the 
clutch  pedal  all  the  way  down  and  move  the  gear  shift  lever  to  first 
speed  position.  The  clutch  should  be  allowed  to  engage  gradually 


300  MOTOR  VEHICLES  AND  THEIR  ENGINES 

and  at  the  same  time  the  throttle  should  be  opened  sufficiently  to 
prevent  stalling,  but  not  cause  racing  of  the  engine.  If  the  foot 
brake  has  been  employed  it  should  be  released  as  the  clutch  is  en- 
gaged. After  the  clutch  has  fully  engaged  the  throttle  should  be 
opened  sufficiently  to  accelerate  the  car  to  change  to  the  next  higher 
speed.  The  throttle  should  be  controlled  by  the  foot  accelerator 
pedal.  Once  the  car  is  in  motion  the  driver  must  at  all  times  keep 
his  eyes  on  the  road  in  the  direction  in  which  the  car  is  moving  or 
about  to  move  when  changing  direction. 

TO  SHIFT  GEARS  (Increasing  Speed) 

Before  starting  a  driver  should  practice  moving  the  gear  shift 
lever  to  the  different  positions  and  getting  his  feet  and  hands  ac- 
customed to  the  location  of  the  foot  pedals  and  hand  levers.  Then 
it  will  not  be  necessary  to  look  away  from  the  road  in  order  to  shift 
gears  or  in  any  other  way  to  control  the  operation  of  the  car.  To 
change  gears  the  clutch  pedal  should  be  depressed  (it  may  not  be 
necessary  to  push  it  all  the  way  down  against  the  floor  boards)  and 
the  foot  removed  from  the  accelerator  pedal  at  the  same  time.  Move 
the  gear  shift  lever  from  first  to  neutral  position,  pausing  if  neces- 
saryi,  and  then  move  to  second  speed  position.  Engage  the  clutch 
immediate!^  and  open  the  throttle  either  with  hand  or  foot  control 
as  soon  as  the  clutch  is  engaged.  The  process  of  changing  from 
second  to  third  or  from  third  to  fourth  is  identical.  Bear  in  mind 
that  before  each  change  is  made  the  speed  of  the  car  should  be 
accelerated.  Care  should  be  taken  when  changing  from  a  lower  to  a 
higher  speed  that  the  car  is  moving  at  a  sufficient  rate  of  speed  so 
that  an  undue  strain  will  not  be  put  on  the  engine.  Practice  alone 
in  driving  the  particular  apparatus  will  acquaint  the  driver  with  the 
necessary  speed  required  to  change  from  one  gear  ratio  to  another. 

TO  SHIFT  GEARS  (Decreasing  Speed) 

When  it  is  desired  to  change  from  a  higher  to  a  lower  gear  ratio 
release  the  clutch  and  allow  the  hand  or  foot  throttle  control  to  re- 
main open  far  enough  so  that  the  engine  will  speed  up.  Move  the 
gear  shift  lever  to  the  neutral  position  and  again  engage  the  clutch 
for  an  instant.  Release  the  clutch  immediately  and  quickly  move 
the  gear  shift  lever  from  neutral  to  the  next  lower  speed  position 
and  engage  the  clutch  immediately,  opening  the  throttle  by  the  hand 
or  foot  control. 

Another  method  of  shifting  to  a  lower  gear  ratio  is  to  leave  the 


HOW  TO  DRIVE  301 

throttle  open  and  release  the  clutch  just  enough  to  allow  it  to  slip 
and  the  engine  to  speed  up.  The  gear  shift  lever  should  then  be 
moved  through  neutral  directly  to  the  next  lower  speed  position  and 
the  clutch  engaged.  This  method  does  not  require  as  much  practice 
but  is  objectionable  since  it  wears  or  burns  the  clutch  facing. 

TO  STOP  THE  CAR 

To  stop  the  car  the  throttle  should  be  closed,  the  clutch  released, 
and  the  brakes  applied,  all  being  performed  at  the  same  time.  The 
amount  of  pressure  applied  at  the  brake  pedal  depends  upon  the  dis- 
tance in  which  the  driver  desires  to  stop  the  car.  Before  allowing 
the  clutch  to  engage  after  the  car  has  stopped,  move  the  gear  shift 
lever  to  the  neutral  position.  If  the  car  is  to  stand  apply  the  emer- 
gency brakes.  If  the  engine  is  to  be  stopped  speed  it  up  by  opening 
the  throttle  just  before  turning  the  ignition  switch  to  the  "off" 
position.  If  the  weather  is  cold  use  the  choke  when  stopping  the 
engine  or  set  dash  adjustment  to  give  a  rich  mixture.  This  will 
make  starting  easier  if  the  engine  is  started  within  a  reasonable 
length  of  time. 

DRIVING  SUGGESTIONS 

In  operating  a  car  it  is  always  best  to  alternate  the  service  and 
emergency  brakes  rather  than  to  use  one  continuously,  to  equalize 
the  wear  on  them.  When  approaching  a  very  steep  down  grade  it 
is  safest  to  move  the  gear  shift  lever  to  a  lower  speed  position,  closing 
the  throttle  and  permitting  the  car  to  drive  the  engine.  When  the 
grade  is  not  excessively  steep  the  engine  can  be  used  as  a  brake  with 
the  position  of  the  gear  shift  lever  remaining  unchanged.  This  will 
save  the  brakes  and  tend  to  cool  the  engine.  The  brakes  should 
never  be  applied  suddenly  enough  to  slide  the  driving  wheels  except 
in  cases  of  emergency.  When  a  stop  is  to  be  made  apply  the  brakes 
soon  enough  so  that  the  motion  of  the  car  will  be  gradually  di- 
minished and  brought  to  a  stop  at  the  point  desired. 

To  avoid  accidents  on  the  road  all  rules  and  regulations  governing 
the  driving  of  motor  vehicles  on  the  road  should  be  observed.  When 
turning  corners  or  approaching  cross  roads  warning  should  be  given 
to  avoid  collision  with  other  vehicles  which  may  be  hidden  from  the 
view  of  the  driver.  Before  backing  the  machine  the  driver  should 
be  sure  the  road  is  clear.  In  manipulating  the  car  the  front  wheels 
should  never  be  turned  by  moving  the  steering  wheel  when  the  car 
is  not  in  motion.  This  puts  undue  strain  on  the  steering  apparatus 


302  MOTOR  VEHICLES  AND  THEIR  ENGINES 

and  will  cause  lost  motion  in  the  steering  gear.  If  it  becomes  neces- 
sary to  turn  the  front  wheels  of  a  car  while  it  is  standing  still,  they 
should  be  moved  by  applying  force  not  only  to  the  steering  wheel 
but  also  by  pulling  the  front  wheels  around. 

When  a  car  skids  the  tendency  is  for  an  inexperienced  driver  to 
apply  the  brakes  and  turn  the  front  wheels  in  the  opposite  direction 
to  that  in  which  he  is  skidding.  This  should  not  be  done  as  it  only 
accentuates  the  skidding  and  the  car  may  be  ditched  or  skid  into 
another  vehicle  or  the  curbing.  When  the  machine  starts  to  skid 
turn  the  steering  wheels  in  the  direction  in  which  the  car  is  skidding 
and  partially  close  the  throttle  but  not  entirely,  or  it  will  have  the 
same  effect  as  applying  the  brakes.  When  the  car  straightens  out 
the  power  may  be  again  applied  gradually  and  the  machine  brought 
back  to  the  center  of  the  road.  When  skidding  on  narrow  roads  it 
is  best  to  apply  the  power  and  steer  for  the  center  of  the  road.  This 
will  aggravate  the  skid  for  a  moment  but  brings  the  machine  around 
at  an  angle  with  the  front  wheels  in  the  center  of  the  road.  The 
momentum  of  the  car  will  cause  the  rear  wheels  to  climb  back  onto 
the  road  again. 


CHAPTER  XXIX 


ENGINE  TROUBLES  EXPERIENCED  ON  THE  ROAD 

If  the  engine  will  not  start  when  the  driver  wants  to  take  the 
machine  from  the  parking  space  it  is  a  very  difficult  matter  to  locate 
the  trouble  and  it  can  only  be  located  by  a  systematic  search.  It  is 
always  best  to  look  over  the  ignition  system  first,  then  see  if  there  is 
any  gasoline  at  the  carburetor.  It  will  often  take  some  time  to  find 
the  trouble.  However,  if  the  engine  once  starts  there  is  no  reason  for 
difficulty  in  locating  the  trouble  as  there  will  always  be  an  indication 
which  should  point  to  the  source  of  the  trouble.  The  great  difficulty 
with  inexperienced  drivers  is  that  they  do  not  reason  out  the  matter 
carefully  before  attempting  to  remedy  it.  Also  an  inexpereinced  man 
usually  looks  for  all  troubles  in  the  same  place  no  matter  what  the 
indication.  Nearly  all  the  difficulties  experienced  with  the  engine 
arise  from  one  of  three  sources;  ignition,  carburetion,  or  engine. 
These  are  outlined  in  the  following  table.  The  method  of  determin- 
ing the  trouble  and  remedy  is  explained  at  the  end  of  the  table.  The 
trouble  is  located  by  the  indication  it  gives  the  driver. 

I.   Engine  Misses : 

A.  Ignition. 

1.  Plugs. 

a.  Short  circuited. 

b.  Broken  porcelain. 

c.  Too  large  a  gap. 

2.  Cable. 

a.  Broken. 

b.  Grounded. 

3.  Instrument. 

a.  Dirty  distributor. 

b.  Interrupter  points  (On  Magneto). 

B.  Carburetor. 

1.  Water  in  the  carburetor. 

2.  Dirt  in  the  line. 

3.  No  pressure  or  no  gas. 

4.  Too  lean  a  mixture. 

C.  Engine. 

1.  Cold. 

2.  Valves  sticking. 

303 


304  MOTOR  VEHICLES  AND  THEIR  ENGINES 

II.   Back  Fires  Through  the  Carburetor: 

A.  Ignition. 

1.  Wired  wrong. 

2.  Timed  wrong. 

B.  Carburetor. 

1.  Water  in  carburetor. 

2.  Dirt  in  the  line. 

3.  No  pressure  or  no  gas. 

4.  Too  lean  a  mixture. 

C.  Engine. 

1.   Valve  sticking  (Inlet), 

III.    Engine  Knocks: 

A.  Ignition. 

1.   Too  far  advanced. 

B.  Engine. 

1.  Carbonized  cylinders  (pre-ignition) 

2.  Overheated  engine. 

3.  Loose  bearings. 

4.  Loose  pistons. 

IV.   Engine  Lacks  Power : 

A.  Ignition. 

1.   Retarded  spark. 

B.  Carburetor. 

1.   Too  rich  a  mixture. 

C.  Engine. 

1.  Exhaust  valve  not  seating. 

2.  Carbon  in  cylinder. 

3.  Overheated  engine. 

4.  Lack  of  lubrication. 

5.  Governor  connections  sticking. 

D.  Brakes. 

1.   Dragging. 

E.  Clutch. 

1.   Slipping. 

V.   Engine  Overheats: 

A.  Ignition. 

1.   Retarded  spark. 

B.  Carburetor. 

1.   Rich  mixture. 


ENGINE  TROUBLES  EXPERIENCED  ON  THE  ROAD          305 

C.     Engine. 

1.  Cooling  system. 

a.  Fan  belt  off. 

b.  No  water. 

c.  No  circulation. 

d.  Anti-freezing  mixture. 

2.  Carbonized  cylinders. 

3.  Lack  of  lubrication. 

VI.    Engine  Stops: 

A.  Engine  and  Car  Stop  gradually. 
1.   Trouble  with  fuel. 

B.  Engine  and  Car  stop  suddenly. 
1.   Mechanical  trouble. 

C.  Engine  stops  suddenly,  car  gradually. 
1.   Trouble  with  ignition. 

VII.    Engine  Won't  Stop: 

A.  Ignition. 

1.  Cable. 

2.  Switch. 

B.  Pre-ignition. 

1.  Carbon  in  cylinders. 

2.  Overheated  engine. 

Now  consider  how  each  of  these  indications  may  differ  so  that  it 
is  possible  to  locate  the  exact  source  of  trouble  without  first  investi- 
gating. If  a  car  has  been  on  the  road  for  some  time  and  the  engine 
misses  it  will  either  miss  regularly  in  one  or  more  cylinders  or  irregu- 
larly in  all  cylinders.  If  the  former  the  miss  is  due  to  ignition.  The 
cylinder  in  which  the  miss  is  occurring  can  be  easily  determined  by 
short  circuiting  each  plug  with  a  screw  driver.  This  is  done  by  al- 
lowing the  screw  driver  to  touch  the  central  electrode  of  the  plug  and 
also  the  engine.  When  a  plug  is  short-circuited,  and  it  does  not  affect 
the  operation  of  the  engine,  it  shows  that  there  was  no  spark  jumping 
across  the  electrodes  of  the  plug.  If  the  cable  to  this  plug  is  dis- 
connected and  held  a  short  distance  from  the  central  electrode  of  the 
plug  from  which  it  was  removed,  a  spark  will  or  will  not  jump  this  gap. 
If  it  does  jump  the  gap  it  shows  that  the  plug  is  short-circuited.  The 
plug  is  either  carbonized  or  the  insulator  is  broken.  If  a  spark  does 
not  occur  place  the  cable  near  the  engine  and  if  a  spark  occurs  it 
shows  that  the  gap  was  too  large  at  the  electrodes  of  the  plug.  If  no 
spark  occurs  it  shows  that  the  trouble  is  not  in  the  plug  but  at  some 


306    .  MOTOR  VEHICLES  AND  THEIR  ENGINES 

point  ahead  of  this.  If  the  engine  is  firing  on  all  but  one  cylinder  the 
trouble  must  be  some  place  between  the  distributor  rotor  and  the 
plug.  First  see  if  the  distributor  is  dirty  and  then  check  up  the 
cable  to  see  if  it  is  broken  or  grounded.  One  point  to  be  remembered 
is  that  the  parts  of  the  magneto  or  battery  ignition  system  incorpora- 
ted in  the  instruments  will  effect  the  operation  on  all  cylinders  and 
there  is  no  need  of  looking  for  the  trouble  there  if  only  one  cylinder 
misses.  If  every  other  cylinder  to  fire  misses  and  magneto  ignition  is 
used,  it  is  often  due  to  the  timing  lever  housing  being  jammed  over  to 
one  side  so  that  the  interrupter  points  are  opened  only  by  one  cam. 
In  no  case  is  it  necessary  to  file  the  interrupter  points  to  overcome  a 
miss  for  the  interrupter  affects  the  operation  on  every  cylinder  and  not 
one. 

If  the  miss  is  irregular  it  is  due  to  carburetor  or  fuel  troubles.  To 
locate  the  trouble  open  the  pet  cock  at  the  bottom  of  the  carburetor 
and  if  there  is  any  water  in  the  carburetor  it  will  run  out.  This  opera- 
tion also  shows  whether  the  gasoline  runs  freely.  If  it  does  not  there 
may  be  dirt  in  the  line  or  no  gasoline  supply.  After  everything  else 
has  been  tried  to  overcome  the  trouble  adjust  the  carburetor  to  com- 
pensate for  too  lean  a  mixture. 

When  an  engine  is  first  started  it  will  often  miss.  This  is  due  to  the 
engine  being  cold.  Under  no  circumstance  should  time  be  wasted  to 
overcome  missing  until  the  engine  is  warm.  If  an  exhaust  valve 
sticks  it  will  cause  the  engine  to  miss  as  the  gases  will  be  forced  out  on 
the  compression  stroke.  This  is  difficult  to  locate  as  it  is  a  regular 
miss  but  usually  results  from  an  overheated  engine. 

If  an  engine  back-fires  when  first  started  and  does  so  continuously 
it  is  best  to  check  up  the  wiring  and  timing  of  the  ignition  system. 
If  the  engine  is  running  smoothly  and  suddenly  starts  to  back-fire 
through  the  carburetor  it  is  possible  that  the  magneto  coupling  has 
slipped. 

If  there  is  water  in  the  carburetor  it  may  suddenly  shut  off  the 
supply  of  gasoline  and  cause  so  lean  a  mixture  that  back-firing  results. 
Dirt  in  the  line  or  running  out  of  gasoline  would  have  the  same 
effect.  If  back-firing  into  the  carburetor  is  experienced  in  addition 
to  missing  of  the  engine  it  is  probably  due  to  too  lean  a  mixture. 
Back-firing  also  results  from  the  inlet  valve  sticking  or  not  seating 
properly. 

If  the  engine  suddenly  develops  a  knock  while  in  operation  it 
may  be  due  to  the  ignition  being  too  far  advanced  for  the  condition 
under  which  the  car  is  operating  and  the  spark  lever  should  be 
retarded.  This  will  be  noticed  mostly  when  the  car  is  under  a  hard 
pull  such  as  on  hills  or  when  going  through  sandy  roads.  If  the 


ENGINE  TROUBLES  EXPERIENCED  ON  THE  ROAD          307 

engine  develops  a  knock,  after  having  been  run  for  a  short  while, 
which  cannot  be  overcome  by  retarding  the  spark  it  may  be  due  to 
carbon  in  the  cylinders  or  an  overheated  engine  both  of  which  would 
cause  pre-ignition  of  the  charge.  By  pre-ignition  is  meant  that  the 
incoming  charge  when  under  compression  is  ignited  due  to  the  heat 
in  the  cylinder  regardless  of  when  the  ignition  spark  takes  place. 
Loose  bearings  and  loose  pistons  will  cause  knocks  but  these  should 
easily  be  distinguished  from  ignition  knocks  as  they  are  present  at 
all  times. 

If  the  engine  shows  a  lack  of  power  it  may  be  "that  the  ignition 
system  is  too  far  retarded  due  to  the  coupling  driving  the  magneto 
having  slipped.  If  too  rich  a  mixture  is  used  it  will  cause  a  loss  of 
power  but  can  easily  be  discovered  by  the  black  smoke  which  is 
given  off  at  the  exhaust  pipe.  Every  precaution  should  be  taken  to 
locate  the  trouble  when  an  engine  shows  a  lack  of  power  as  it  may  be 
caused  from  the  valves  not  seating  properly,  carbon  in  the  cylinders, 
overheated  engine,  lack  of  lubrication,  or  the  governor  connection 
sticking.  If  lack  of  lubrication  is  causing  the  trouble  it  will  soon 
lead  to  mechanical  troubles  such  as  scoring  of  the  cylinder  walls  or 
burning  out  the  bearings.  An  engine  will  often  give  an  apparent 
indication  of  a  lack  of  power  due  to  the  brakes  dragging  or  the  clutch 
slipping. 

If  an  engine  overheats  it  is  best  to  check  up  and  see  whether  or 
not  the  car  is  being  operated  on  a  retarded  spark  or  if  the  mixture  is 
too  rich.  The  usual  causes  of  the  engine  overheating  are  troubles 
experienced  with  the  cooling  system.  Fan  belts  often  break  or  slip, 
the  water  may  have  leaked  out  some  place  in  the  cooling  system,  or 
the  circulation  may  be  stopped  in  some  way.  If  anti-freezing  mix- 
tures are  allowed  to  remain  in  the  cooling  system  in  warm  weather 
they  will  cause  overheating  of  the  engine  due  to  their  low  conductivity 
of  heat.  Carbon  in  the  cylinders  causes  the  engine  to  overheat  and 
is  deterimental  to  its  operation.  If  the  engine  is  not  lubricated 
properly  it  will  overheat  due  to  the  additional  friction  of  the 
parts. 

If  after  the  car  is  in  operation  the  car  and  engine  slow  down 
gradually  the  trouble  is  without  doubt  due  to  a  lack  of  fuel  or  some 
trouble  with  the  fuel  system  or  carburetor.  When  the  car  stops 
under  these  conditions  the  engine  usually  back-fires  into  the  carbure- 
tor just  before  the  car  stops. 

If  the  car  and  engine  stop  suddenly  it  is  an  indication  of  some 
mechanical  trouble  such  as  a  frozen  bearing,  broken  connecting  rod, 
or  some  other  part  which  suddenly  puts  a  brake  on  the  movement  of 
the  car. 


308  MOTOR  VEHICLES  AND  THEIR  ENGINES 

If  the  engine  suddenly  stops  operating  and  the  car  continues  to 
coast  the  trouble  can  be  traced  to  the  ignition  system.  A  discon- 
nected or  broken  wire  usually  causes  the  trouble. 

If  the  engine  will  not  stop  when  the  ignition  switch  is  thrown  to 
the  "off"  position  it  is  possible  with  magneto  ignition  that  the  cable 
between  the  magneto  and  switch  is  disconnected.  That  is,  the  switch 
does  not  connect  the  primary  of  the  magneto  to  the  ground.  If  the 
engine  is  overheated,  due  to  lack  of  proper  cooling  or  carbon  in  the 
cylinders,  the  engine  will  continue  to  operate  due  to  the  pre-ignition. 


CHAPTER  XXX 


LUBRICATION  £ 

Lubrication  is  the  principal  problem  in  the  care  and  upkeep  of  the 
motor  vehicle.  If  proper  lubrication  is  maintained  a  great  part  of 
the  work  required  to  keep  a  motor  vehicle  in  good  condition  has  been 
accomplished. 

Before  taking  up  the  use  of  lubricants  the  purpose  and  reason  for 
their  use  should  be  understood.  Whenever  any  two  metal  surfaces 
rub  against  each  other  such  as  a  shaft  in  a  bearing  or  two  gear  teeth 
meshing  together  there  is  friction  no  matter  how  highly  polished  the 


Fig.  273 — Magnified  Bearing  Surface 

surfaces.  If  the  surfaces  were  examined  under  a  microscope  they 
would  appear  to  be  covered  with  minute  irregularities  (Fig.  273). 
These  irregularities  if  allowed  to  rub  on  each  other  would  cause  a 
loss  of  power  and  considerable  wear  and  the  heat  set  up  would  cause 
them  to  bind. 


310  MOTOR  VEHICLES  AND  THEIR  ENGINES 

To  prevent  this  condition  some  substance  usually  a  layer  of  oil  or 
grease  called  a  lubricant  is  placed  between  the  surfaces  to  separate 
them.  The  lubricant  consists  of  a  vast  number  of  minutely  dimen- 
sioned balls  composed  of  fat  and  tied  together  by  a  mother  liquor 
which  maintains  their  separation.  All  the  motion  and  rubbing  comes 
between  these  balls  of  fat  which  are  not  hard  like  metal  and,  therefore, 
rub  against  each  other  with  but  little  friction. 

It  is  not  enough  to  place  the  lubricating  film  between  the  surfaces, 
it  must  be  kept  there.  To  do  this  it  is  necessary  to  choose  a  lubricant 
that  has  the  required  properties  to  withstand  the  conditions  under 
which  it  has  to  perform  its  duties.  For  this  reason  lubricants  are 
rated  in  accordance  with  certain  tests  such  as  viscosity,  flash  point, 
fire  point,  cold  point,  and  specific  gravity. 

Viscosity  or  fluidity  of  the  lubricant  is  one  of  the  most  important 
things  to  be  considered  in  its  selection.  If  the  lubricant  flows  too 
easily  it  will  run  out  at  the  end  of  the  bearing.  Nearly  all  oils  have 
good  viscosity  at  ordinary  temperatures  but  when  heated  they  thin 
out  too  much  and  flow  too  freely.  When  a  lubricant  is  to  be  used  in 
an  engine  the  viscosity  should  be  measured  at  100  degrees  Fahrenheit, 
200  degrees  Fahrenheit,  and  300  degrees  Fahrenheit  to  have  a  lubri- 
cant that  is  neither  too  heavy  at  low  temperatures  nor  too  thin  at 
high  temperatures. 

Specific  Gravity  of  the  lubricant  shows  its  body  or  density.  This 
is  important  for  it  is  necessary  to  have  a  lubricant  that  has  sufficient 
body  to  withstand  the  pressure  to  which  it  is  subjected. 

Flash  Point  of  an  oil  is  the  lowest  temperature  at  which  the  vapors 
arising  from  it  will  ignite.  When  an  oil  is  used  in  an  internal  combus- 
tion engine  and  thus  exposed  to  severe  heat  it  becomes  imperative  to 
use  an  oil  of  high  flash  point.  This  should  not  be  much  below  400 
degrees  Fahrenheit. 

Fire  Point  of  an  oil  is  the  lowest  temperature  at  which  the  oil 
itself  ignites  from  the  burning  of  its  vapors.  Since  the  fire  point  of 
an  oil  is  always  higher  than  the  flash  point  it  is  of  little  value  if  the 
flash  point  is  high. 

Cold  Point  of  an  oil  is  the  lowest  temperature  at  which  the  oil  will 
pour.  This  characteristic  need  only  be  taken  into  consideration 
because  of  its  effect  on  free  circulation  of  oil  through  exterior  feed 
pipes  when  pressure  is  not  applied.  It  also  affects  the  lubricating 
qualities  of  the  oil  until  it  thaws  out. 

These  specifications  must  be  carefully  considered  in  the  selection 
of  a  lubricant  and  the  correct  lubricants  to  use  will  be  specified  in 
the  Lubrication  Tables  in  manufacturer's  catalogues.  When  selecting 
engine  oils  it  is  necessary  to  consider  carefully  the  fire  point,  flash 


LUBRICATION 


311 


point,  and  viscosity.  Bear  in  mind  that  an  air-cooled  engine  re- 
quires a  heavier  oil  and  one  of  a  higher  flash  point  than  a  water- 
cooled  engine.  It  is  also  true  that  m  warm  weather  a  heavier  lubri- 
cant is  necessary  than  in  cold  weather. 

It  is  well  to  consider  the  sources  from  which  lubricants  are  ob- 
tained. The  light  oils  such  as  cylinder  oils  are  almost  always  mineral 
oils.  The  heavier  oils  for  transmissions  are  usually  mineral  oils 
made  by  adding  animal  or  vegetable  fats  to  thicken  them.  The 
greases  are  usually  vegetable  or  animal  substances  of  a  soapy  nature 
with  mineral  oils  added  to  make  them  lubricants.  Greases  are 
usually  of  two  kinds,  cup  grease  and  gear  grease.  The  main  differ- 
ence is  that  cup  grease  will  break  down  into  soap  and  oil  if  heated 
while  gear  grease  will  not. 

There  are  many  methods  used  in  lubricating  an  engine  and  only 
those  most  commonly  found  will  be  discussed.  The  parts  requiring 
lubrication  are  the  main  crank  shaft  bearings,  crank  pin  bearings, 
wrist  pin  bearings,  cam  shaft  bearings,  timing  gears,  cams,  valve 
lifters  and  guides,  pistons,  piston  rings,  and  cylinder  walls.  The 
following  systems  are  employed: 


¥    I 


Fig.  274 — Splash  System 

SPLASH. — The  oil  is  held  in  the  crank  case  being  supplied  either 
by  a  mechanical  oiler  or  direct  from  some  outside  source.  As  the 
engine  turns  over  the  lower  ends  of  the  connecting  rods  or  dippers 
on  the  connecting  rods  strike  the  oil  and  splash  it  in  all  directions. 
This  fills  the  cups  that  supply  the  main  bearings.  The  crank  pin 
bearings  receive  their  oil  through  holes  bored  into  the  bearings. 
When  the  connecting  rods  dip,  the  oil  is  splashed  up  on  the  piston  and 
cylinder  walls.  The  oil  which  is  splashed  to  the  inner  surface  of  the 
piston  will  drop  off  the  lug  (Fig.  274)  and  supply  the  wrist  pin  bearing. 
The  cam  shaft  bearings  and  lifter  rod  bearings  depend  upon  the  splash 
for  obtaining  their  lubrication.  Thus  all  of  the  parts  are  lubricated 
by  the  dipping  of  the  connecting  rods  into  the  lubricant. 


312 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


It  is  important  not  to  let  the  oil  level  get  too  low.  In  putting 
oil  in  the  crank  case  it  is  also  important  not  to  have  it  too  high. 
Too  much  oil  will  cause  carbon  to  be  formed  in  the  cylinders  which 
results  in  fouling  of  the  spark  plugs,  pre-ignition,  overheating,  and 
knocking.  It  also  causes  a  blue  or  white  smoke  at  the  exhaust  which 
should  not  be  confused  with  black  smoke  produced  by  too  rich  a 
mixture. 


Fig.  275 — Splash  with  Circulating  Pump 

SPLASH  WITH  CIRCULATING  PUMP.— This  system  is 
designed  to  overcome  the  difficulty  experienced  with  over-lubrication 
as  in  the  splash  system.  Oil  is  supplied  from  the  reservoir  or  sump, 
by  means  of  a  pump  to  splash  troughs  (Fig.  275) .  These  troughs  are 
designed  to  hold  only  sufficient  oil  for  proper  lubrication  and  will 
overflow  if  too  much  oil  is  supplied  to  them.  In  this  way  the  diffi- 
culty of  over  lubricating  is  reduced  to  a  minimum.  In  every  other 
respect  this  system  is  identical  with  the  splash. 


Fig.  276— Force  Feed  and  Splash 

FORCE  FEED  AND  SPLASH.— Oil  is  forced  by  pump  pressure 
direct  to  the  main  crank  shaft  bearings  (Fig.  276).  The  overflow 
falls  into  the  splash  troughs  in  the  crank  case  into  which  the  con- 
necting rods  dip  and  splash  oil  to  all  other  parts  of  the  engine.  A 


LUBRICATION 


313 


constant  oil  level  is  maintained  in  the  splash  troughs  by  an  overflow 
to  the  sump  or  reservoir  below,  from  which  the  oil  is  again  circulated. 


Fig.  277— Force  Feed 

FORCE  FEED.— The  oil  is  forced  by  pump  pressure  direct  to  the 
main  crank  shaft  bearings  and  then  through  holes  drilled  in  the  crank 
arms  to  the  crank  pin  bearings  (Fig.  277).  As  the  oil  overflows  from 
the  crank  pin  bearings  it  is  thrown  by  centrifugal  force  to  the  cylinder 
walls,  piston  walls,  the  wrist  pin,  and  all  other  parts.  There  is  no 
splash  in  this  system  as  the  connecting  rods  do  not  dip  into  oil.  The 
overflow  of  the  oil  returns  to  the  sump  or  reservoir  and  is  again 
circulated. 


Fig.  278 — Full-Force  Feed 

FULL  FORCE  FEED.— Oil  is  forced  by  pump  pressure  direct  to 
the  main  crank  shaft  bearings  and  through  holes  in  the  crank  arms 
to  the  crank  pin  bearings.  From  here  it  is  led  by  pipes  or  hollow 
connecting  rods  to  the  wrist  pin  bearings  (Fig.  278).  The  cam  shaft 
is  usually  hollow  and  has  its  bearings  supplied  by  the  same  pressure. 
The  piston  and  cylinder  walls  are  supplied  by  oil  thrown  from  the 
lower  ends  of  the  connecting  rods*.  In  some  cases  the  overflow  of 
the  oil  from  the  wrist  pins  is  used  to  assist  in  lubricating  the  piston 
and  cylinder  walls. 


314  MOTOR  VEHICLES  AND  THEIR  ENGINES 

As  it  is  continually  necessary  to  add  more  lubricant  to  the  engine 
it  may  be  necessary  to  change  the  kind  of  oil  used.  If  so,  it  is  best  to 
drain  out  the  old  oil  and  clean  the  crank  case  with  kerosene  and  then 
refill  with  fresh  oil.  The  reason  for  this  is  that  oils  do  not  always 
mix  readily.  When  two  oils  are  shaken  or  stirred  up  as  in  an  engine 
air  bubbles  will  form.  This  causes  a  mixture  of  air  and  oil  to  be 
brought  into  contact  with  the  surfaces  instead  of  all  lubricant. 

Cleaning  and  draining  of  the  crank  case  should  also  be  done  once  a 
month  or  about  every  1,000  miles  of  running.  It  should  be  done  also 
at  the  end  of  the  first  500  and  1,000  miles  run  with  a  new  car.  Drain 
out  the  old  oil  through  the  plug  in  the  bottom  of  the  crank  case  and 
refill  with  about  a  gallon  of  kerosene.  If  the  engine  has  an  electric 
starter  turn  the  engine  over  with  the  starter  for  about  fifteen  seconds. 
If  there  is  no  starter  the  engine  may  be  run  for  about  the  same  length 
of  time.  This  will  thoroughly  clean  out  the  circulating  system  and 
the  kerosene  may  now  be  drained  from  the  crank  case.'  It  is  impor- 
tant that  all  the  kerosene  be  drained  from  the  crank  case  as 
any  that  is  left  will  mix  with  the  new  oil,  reducing  its  lubricating 
qualities.  In  some  engines  such  as  the  Wisconsin  the  splash  par- 
titions in  the  crank  case  will  retain  considerable  kerosene  and  it 
will  be  necessary  to  remove  the  lower  half  of  the  crank-case  to  drain 
thoroughly.  This  removal  gives  a  chance  for  the  inspection  of  the 
pistons,  connecting  rods,  main  bearings,  etc.,  and  advantage  should  be 
taken  of  this  opportunity.  After  the  kerosene  is  thoroughly  drained 
from  the  crank-case  the  oil  strainer  should  be  cleaned  and  replaced 
and  the  crank-case  refilled  to  the  proper  level  with  fresh  oil.  Before 
starting  the  engine  it  is  wise  to  turn  it  over  several  times  by  hand  to 
fill  the  circulating  system  with  fresh  oil.  If  the  oil  circulating  system 
on  the  engine  is  supplied  with  a  pressure  gauge,  excessive  pressure  or 
no  pressure  at  all  at  a  car  speed  of  fifteen  to  twenty-five  miles  an  hour 
indicates  plugging  of  the  oil  circulation  system  and  should  be  investi- 
gated immediately.  The  same  is  true  of  the  stoppage  or  irregular 
action  of  a  sight  feed  if  one  is  supplied.  In  the  case  of  the  White 
(Model  T.  E.  B.  0.)  this  latter  trouble  might  be  due  to  stoppage  in  the 
oil  pump  check  valves  which  should  be  investigated  immediately. 

The  proper  level  for  oil  in  the  transmission  case  is  such  that  all  the 
gears  on  the  upper  shaft  dip  one-half  an  inch  or  so  into  the  oil.  The 
transmission  case  should  be  drained,  cleaned  with  kerosene,  and  re- 
filled every  five  thousand  miles  or  about  twice  a  year.  The  level 
should  be  inspected  monthly. 

A  wet  plate  or  multiple  disc  clutch  should  be  drained  and  cleaned 
with  kerosene  once  a  month  or  every  1,000  miles.  When  cleaning 
with  kerosene  run  the  engine  and  disengage  the  clutch  several  times. 


LUBRICATION  315 

Do  not  use  too  heavy  an  oil  in  the  clutch  as  it  will  cause  it  to  either 
slip,  drag,  or  both. 

Oil  or  grease  may  be  used  in  the  differential  housing.  The  deter- 
mining factor  in  many  cases  is  leakage  of  the  lubricant  from  the 
end  of  the  rear  axle  onto  the  brake  drums.  If  this  is  continuous 
and  cannot  be  stopped  by  the  use  of  a  new  felt  washer  in  the 
rear  axle  it  will  be  advisable  to  mix  some  heavier  grease  with  the 
lubricant  recommended,  to  prevent  this  leakage. 

A  general  rule  may  be  given  for  the  use  of  grease  cups.  Turn  the 
cup  till  the  grease  is  seen  to  start  squeezing  from  the  bearing.  There 
are  of  course  exceptions  to  the  general  rule  such  as  when  the  grease 
might  reach  parts  that  would  be  injured  by  it  or  when  the  cup  is  so 
located  that  no  grease  can  escape.  However,  as  a  general  rule 
grease  cups  are  turned  too  little  rather  than  too  much.  Be  careful 
to  wipe  off  all  excess  grease  as  it  collects  dirt  and  grit  which  may  work 
into  the  bearing  and  cause  damage.  It  is  also  better  to  use  oil  in  place 
of  grease  on  brake  equalizer  slides  and  other  exposed  places  as  it  is  not 
so  liable  to  pick  up  dirt  and  grit. 

It  must  be  remembered  in  handling  grease  cups  that  the  threads 
are  very  fine  and  easily  crossed.  The  cap  must  be  held  square  with 
the  threads  when  starting  to  turn  it  on.  If  the  cap  turns  hard  the 
threads  are  probably  crossed.  The  cap  should  be  backed  off  and  a 
new  start  made.  If  this  is  not  done  the  threads  will  be  stripped  and 
the  cap  spoiled.  The  same  thing  applies  to  grease  guns  which 
usually  have  fine  threads  on  the  cap. 

As  already  stated  gasoline  and  kerosene  are  used  to  wash  out 
lubrication  from  any  part  and  for  this  reason  care  should  be  taken  not 
to  over  prime  an  engine.  If  too  much  gasoline  is  used  when  priming 
an  engine  it  will  wash  the  oil  away  from  the  piston  and  cylinder  walls 
causing  a  loss  of  compression.  This  makes  it  very  hard  to  start  the 
engine  and  if  started  will  often  result  in  scoring  the  cylinders  or 
pistons.  This  is  because  the  oil  in  circulating  to  these  parts  will  often 
require  more  time  than  it  takes  for  the  parts  to  heat  up  and  expand 
due  to  the  additional  friction.  The  proper  method  of  priming  an 
engine  is  to  fill  the  primary  cup  full  and  then  open  the  cock  and  allow 
only  this  amount  to  flow  into  the  cylinder.  Do  not  squirt  it  in  direct 
from  the  oil  can. 

The  following  lubrication  "don'ts"  will  give  some  of  the  necessary 
points  which  must  be  carefully  considered : 

Don't  forget  that  an  air  cooled  engine  requires  heavier  oil  than  a 
water  cooled  engine  because  of  its  higher  operating  temperature. 

Don't  think  that  oil  never  wears  out. 

Don't  judge  the  viscosity  of  an  oil  at  atmospheric  temperature. 


316  MOTOR  VEHICLES  AND  THEIR  ENGINES 

Remember  that  when  oil  passes  through  the  bearings  it  has  a  much 
higher  temperature  than  the  surrounding  air. 

Don't  fill  the  oil  reservoir  above  the  correct  level.  Enough  is 
sufficient,  too  much  causes  trouble. 

Don't  expect  lubricating  oil  to  perform  the  impossible  task  of  cor- 
recting mechanical  defects.  Too  much  clearance  between  piston  and 
cylinder  or  bad  and  leaky  piston  rings  will  surely  fill  the  cylinder  with 
carbon  even  when  the  best  lubricating  oil  is  used. 

Don't  use  a  light  oil  when  a  heavy  oil  is  required,  under  the  im- 
pression that  an  oil  must  be  light  in  order  to  reach  the  parts. 

Don't  use  a  heavy  oil  when  a  light  oil  is  required  such  as  on 
ball  bearings  in  the  magneto. 

Don't  use  grease  which  is  not  semi-fluid  in  transmission  or  dif- 
ferentials. After  the  gears  have  cut  tracks  in  hard  grease  further 
lubrication  is  impossible  and  rapid  wear  will  result. 

Don't  run  the  engine  fast  when  a  car  is  new  and  the  bearings  are 
tight.  Wait  until  the  car  has  made  at  least  500  to  1,000  miles. 

Don't  fill  the  reservoir  by  pouring  oil  into  it  through  a  dirty  or 
sandy  funnel. 

Don't  lose  sight  of  the  fact  that  the  life  of  the  car  depends  upon 
the  proper  lubrication  of  the  parts. 

Don't  forget  that  lubricating  should  be  done  often  and  at  regular 
intervals. 


CHAPTER  XXXI 


CARE  AND  ADJUSTMENT 

To  keep  motor  propelled  vehicles  in  proper  running  condition  it  is 
necessary  that  certain  parts  be  inspected  and  adjusted  at  regular  in- 
tervals. Besides  these  adjustments  certain  repairs  will  be  outlined 
in  this  chapter  which  are  likely  to  become  necessary  under  running 
conditions.  Repairs  which  require  special  tools  and  machinery,  re- 
sulting from  accident  or  other  breakage,  are  not  discussed  in  this 
book. 

TESTING  COMPRESSION.— To  test  the  compression  on  a  warm 
engine  each  cylinder  must  be  considered  separately.  Open  the  pet 
cocks  on  all  the  cylinders  except  the  one  that  is  to  be  tested  and  turn  the 
engine  over  until  the  piston  comes  up  against  compression  in  that  cyl- 
inder. If  the  compression  is  good  the  crank  should  resist  being  turned 
over  and  if  the  pull  on  the  crank  is  released  it  should  fly  back  as  if 
moved  by  a  spring.  Hold  the  crank  up  against  compression  for  ten  or 
fifteen  seconds  and  see  if  the  gas  in  the  cylinder  leaks  out  relieving  the 
pressure.  The  length  of  time  that  the  cylinder  will  hold  compression 
indicates  the  amount  of  leakage.  Try  the  compression  of  each  cyl- 
inder in  turn  and  see  if  it  is  the  same  in  all.  Loss  of  compression  is 
due  to  the  gas  leaking  out  of  the  cylinder  and  these  leaks  are  of  three 


1.  Past  various  joints  such  as  cylinder  head  gasket,  valve  cap, 
spark  plug,  priming  cock,  etc. 

2.  Past  pistons  and  piston  rings. 

3.  Past  valves. 

Leaks  of  the  first  class  can  usually  be  detected  by  the  hissing 
sound  of  the  escaping  gas  around  the  joints  and  may  be  located  by 
running  oil  around  these  joints  and  watching  for  bubbles  as  the  engine 
is  turned  by  hand  or  run  slowly.  Leaks  through  the  cylinder  head 
gasket  can  be  detected  by  the  above  method  unless  the  leak  is  into  the 
water  jacket.  This  may  be  detected  by  the  presence  of  water  in  the 
cylinders  after  the  engine  has  been  idle  for  some  time  or  by  listening 
at  the  radiator  cap  for  the  noise  of  the  gas  gurgling  into  the  water. 

Leaks  of  the  second  class  should  be  tested  for  after  determining 
that  the  leak  is  not  of  the  first  class  by  putting  a  couple  of  tablespoon- 
fuls  of  heavy  oil  in  the  leaking  cylinder  and  determining  whether  the 
compression  has  been  improved.  If  this  does  not  improve  the  com- 

317 


318  MOTOR  VEHICLES  AND  THEIR  ENGINES 

pression  it  shows  that  the  leak  must  be  past  the  valves.  Such  leaks 
may  be  due  to  improper  adjustment  of  the  valve  tappets,  to  a  valve 
sticking,  or  to  a  valve  which  is  warped  or  does  not  seat  properly.  In 
the  latter  case  the  valve  will  probably  have  to  be  ground. 

ADJUSTING  VALVE  TAPPETS.— Most  engines  are  provided 
with  adjusting  nuts  for  regulating  the  clearance  between  the  valve 
stem  and  the  push  rod.  The  different  instruction  books  and  the  Care 
and  Adjustment  Tables  in  the  next  chapter  give  the  proper  "cold" 
clearance  for  the  different  engines  on  the  cars  used  in  the  service. 
When  measuring  valve  clearance,  be  sure  that  the  valve  whose  clear- 
ance is  to  be  tested  is  in  the  closed  position.  If  the  piston  of  one  cyl- 
inder is  placed  at  top  dead  center  on  compression  both  valves  will  be 
closed  and  their  clearance  may  be  tested.  Another  good  method  is  to 
turn  the  engine  over  by  hand  until  one  valve  is  wide  open  and  then 
turn  another  full  revolution.  The  valve  will  now  be  closed  and  the 
nose  of  the  cam  on  the  cam  shaft  will  be  pointing  directly  away  from 
the  tappet.  After  the  valve  is  closed,  select  a  gauge  of  the  proper 
thickness  and  slip  it  between  the  valve  stem  and  the  push  rod.  Ad- 
just the  adjusting  nut  so  that  the  gauge  will  just  slip  freely  between 
the  two  and  tighten  the  locknut.  In  tightening  this  nut,  be  sure  that 
the  adjustment  is  not  changed  and  the  nut  is  tight.  Check  the  clear- 
ance after  the  adjustment  is  set.  If  a  thickness  gauge  is  not  available 
one  can  be  made  of  several  thicknesses  of  paper  remembering  that  the 
paper  in  this  book  is  about  0.003  inch  thick.  In  case  the  cold  clear- 
ance is  not  known  the  clearance  may  be  checked  while  the  engine  is 
hot.  The  engine  should  be  run  until  thoroughly  warm  and  the  ad- 
justment made  to  allow  a  perceptible  amount  of  play.  This  should  be 
just  enough  to  show  that  there  is  play  and  no  more.  The  object  of 
this  play  is  to  allow  for  further  heating  of  the  engine,  for  a  small 
amount  of  wear  on  the  valve  at  its  seat,  and  to  insure  that  the  tappet 
is  not  preventing  the  valve  from  seating.  When  valves  are  adjusted 
for  cold  clearance  it  is  best  to  use  this  method  of  checking  their 
clearance.  If  after  checking  the  valve  clearance  the  compression 
leaks  past  the  valves  they  should  be  ground. 

VALVE  GRINDING.— To  grind  a  valve  first  remove  the  valve 
cap  or  drain  the  radiator  and  remove  the  cylinder  head  cover.  Lift 
the  valve  spring  with  a  valve  lifter  tool  and  remove  the  valve  spring 
retainer,  lifting  out  the  valve.  Remove  the  spring  and  turn  down 
the  valve  tappet  adjusting  screw  so  as  not  to  interfere  with  the  valve 
stem.  Clean  the  carbon  from  the  valve  and  from  around  its  seat. 
If  a  valve  is  very  badly  pitted,  if  the  head  is  warped  or  out  of  line  with 
its  seat,  or  if  shoulders  appear  on  the  face  of  its  seat,  the  valve  should 
be  refaced  by  a  mechanic  with  the  proper  tools  before  grinding.  Place 


CARE  AND  ADJUSTMENT  319 

some  waste  or  a  piece  of  cloth  in  the  gas  passage  and  in  the  passage 
to  the  cylinder  to  prevent  the  grinding  compound  from  getting  into 
these  places  and  place  a  little  valve  grinding  compound  on  the  face  of 
the  valve.  This  compound  comes  in  coarse,  medium,  and  fine  grades, 
Unless  the  valve  is  badly  pitted  the  medium  grade  should  be  used 
first  and  the  grinding  finished  with  the  fine.  Be  sparing  of  the  com- 
pound and  do  not  plaster  the  rest  of  the  valve  head  with  it.  The 
compound  should  be  put  on  in  a  smooth  coat.  Put  a  light  spring 
under  the  valve  head  when  replacing  it  in  its  seat  to  lift  the  valve  off 
its  seat  when  the  pressure  used  in  grinding  is  removed.  With  a  screw- 
driver or  brace  turn  the  valve  about  a  half  turn  first  to  the  right  and 
then  to  the  left,  exerting  about  three  or  four  pounds  downward  pres- 
sure. At  frequent  intervals  let  the  valve  lift  off  its  seat  and  turn  it  to 
a  new  position  before  reseating.  Continue  the  oscillating  motion  as 
before  until  a  silvery  band  appears  completely  around  the  valve. 
There  should  be  no  pits  or  breaks  in  this  band  and  the  grinding  should 
be  continued  until  this  is  accomplished.  This  band  need  not  be  over 
Vie  inch  to  3/32  inch  wide.  After  the  band  is  established  a  smooth 
finish  should  be  given  the  surfaces  using  the  fine  grinding  compound. 
Make  sure  that  none  of  it  gets  into  the  cylinder,  gas  passages,  or  valve 
stem  guide.  Valve  grinding  requires  patience  and  persistence  to  do 
good  work.  Be  very  careful  in  grinding  valves  not  to  interchange 
them  nor  put  the  wrong  valve  in  the  wrong  seat,  as  it  will  not  make  a 
gas  tight  joint.  The  exhaust  valves  being  exposed  to  the  hot  gases 
will  require  grinding  much  more  often  than  the  inlet  valves.  After 
the  valves  are  ground  they  may  be  replaced,  the  spring  and  spring 
retainer  put  in  place,  and  the  valve  tappet  adjusted. 

CARBON  REMOVAL. — If  carbon  becomes  excessive  it  causes 
overheating  of  the  engine,  lack  of  power,  pre-ignition,  and  a  tendency 
for  explosions  to  continue  after  the  ignition  switch  has  been  turned  off. 

The  cylinders  can  be  kept  reasonably  free  of  carbon  by  removing 
the  spark  plugs  and  introducing  a  tablespoonful  of  kerosene  in  each 
cylinder  about  once  a  week.  The  kerosene  should  be  inserted  when 
the  engine  is  hot  and  the  best  results  will  be  obtained  by  placing  it 
in  the  cylinders  at  night  in  order  that  it  may  have  an  opportunity 
to  soften  the  carbon  deposit  before  the  engine  is  used  again. 

If  the  engine  has  been  run  for  some  time  without  cleaning  out  the 
cylinders  it  is  well  to  pour  about  a  pint  of  kerosene  through  the  air 
intake  of  the  carburetor  with  the  engine  hot  and  running  at  high 
speed  and  the  spark  lever  fully  retarded.  Do  not  choke  the  engine 
with  the  kerosene  but  pour  it  in  as  fast  as  the  engine  will  take  it  and 
run.  After  this  operation  place  a  tablespoonful  of  kerosene  in  each 
cylinder  and  allow  the  engine  to  stand  idle  for  ten  or  twelve  hours. 


320  MOTOR  VEHICLES  AND  THEIR  ENGINES 

If  an  excessive  amount  of  carbon  has  accumulated  in  the  cylinders 
kerosene  will  not  remove  it.  It  can  then  be  removed  in  one  of  several 
ways.  It  can  be  scraped  out  by  removing  the  cylinder  head  casting 
or  valve  caps,  it  may  be  loosened  and  blown  out  through  the  exhaust 
by  the  use  of  a  carbon  removing  chain  in  the  cylinder,  it  may  be  dis- 
solved out  with  a  carbon  remover,  or  it  may  be  burned  out  with 
oxygen. 

If  the  cylinder  head  is  removable  it  is  an  easy  matter  to  remove 
the  carbon  by  scraping.  Turn  the  engine  over  until  the  piston  in  the 
cylinder  to  be  scraped  is  at  top  dead  center  on  compression  stroke. 
This  prevents  loose  carbon  from  getting  into  the  valve  parts  and 
reduces  to  a  minimum  the  amount  of  carbon  getting  in  between  the 
piston  and  cylinder  walls.  All  holes  in  the  cylinder  block  such  as 
water  jackets  and  stud  holes  should  be  packed  with  waste. 

It  is  very  difficult  to  remove  carbon  by  scraping  through  valve 
cap  holes.  Special  scrapers  are  required  for  scraping  the  cylinder 
head  and  the  top  of  the  piston.  They  must  be  worked  back  and 
forth  over  the  surface  with  considerable  pressure  until  the  scratching 
sensation  stops  and  the  tool  seems  to  glide  freely  over  the  surface. 
Be  very  careful  not  to  scratch  the  surface.  Blow  out  the  carbon  at 
frequent  intervals  with  an  air  hose  if  possible  or  with  a  hand  bellows 
if  compressed  air  is  not  available.  Be  sure  to  scrape  the  entire  inner 
surface  of  the  combustion  space  and  do  not  leave  any  jagged  patches 
as  they  will  become  incandescent  and  cause  pre-ignition.  Continue 
scraping  until  the  air  does  not  blow  out  any  more  carbon  dust. 
The  same  precautions  should  be  taken  regarding  keeping  the  valves 
closed  and  dust  out  of  the  cylinders  as  when  the  cylinder  head  is 
removable. 

After  carbon  has  been  scraped  and  as  much  as  possible  blown  out 
pour  about  a  half  a  glassful  of  kerosene  into  the  cylinder  and  apply 
the  air  blast.  This  should  remove  the  remaining  carbon.  Another 
half  glassful  should  now  be  poured  into  the  cylinder  and  the  engine 
turned  over  several  times  by  hand.  This  will  remove  any  carbon 
which  may  have  worked  down  between  the  piston  and  the  cylinder. 
The  crank  case  should  now  be  drained  and  washed  with  kerosene 
and  refilled  with  fresh  oil. 

When  using  a  carbon  removing  chain  it  should  be  placed  in  posi- 
tion on  top  of  the  piston  through  the  exhaust  valve  cap  opening. 
Remove  the  spark  plug  and  inject  into  the  cylinder  about  two  table- 
spoonfuls  of  kerosene.  The  chain  used  should  be  joined  at  its  ends 
and  should  be  made  of  spring  steel  or  piano  wire  which  is  hard  but 
not  brittle.  The  links  should  not  exceed  %  inch  in  diameter  and 
the  total  length  should  be  about  twelve  inches.  Screw  back  the 


CARE  AND  ADJUSTMENT  321 

valve  cap  leaving  out  the  spark  plug  and  run  the  engine  for  several 
minutes.  The  carbon  loosed  by  the  chain  will  be  blown  out. 

To  use  liquid  carbon  remover,  remove  the  valve  caps  and  turn  two 
cylinders  to  top  dead  center.  This  should  be  done  when  the  engine 
is  warm.  Put  the  carbon  remover  in  these  two  cylinders  allowing  it 
to  remain  for  about  an  hour  and  then  remove  it  by  syphoning. 
The  combustion  chamber  should  now  be  dried  out  as  well  as  possible 
with  a  dry  cloth.  Repeat  the  same  process  in  the  other  pair  of 
cylinders.  This  method  is  not  as  effective  as  scraping  or  burning  out 
the  carbon. 

In  burning  out  the  carbon  one  piston  is  brought  to  top  dead  center 
on  compression,  the  spark  plug  and  one  of  the  valve  caps  removed, 
and  a  small  piece  of  burning  waste  dropped  into  the  cylinder. 
The  operator  then  directs  a  jet  of  oxygen  on  the  carbon  at  the  point 
where  the  waste  is  burning.  This  causes  the  carbon  to  burn  rapidly 
and  to  be  entirely  consumed.  By  following  the  burning  carbon 
around  the  cylinder  with  the  jet  of  oxygen  it  will  be  evenly  burned 
out.  Care  must  be  taken  to  have  the  cooling  system  full  of  water 
while  the  carbon  is  being  burned  to  prevent  overheating  of  the 
cylinder  casting. 

When  scraping  can  be  conveniently  done  it  is  probably  the  best 
method  but  on  some  engines  it  is  difficult  to  accomplish  without 
dismantling.  The  burning  out  method  is  also  good  when  done  care- 
fully by  an  experienced  operator.  The  chain  method  and  the  use  of 
decarbonizing  liquids  are  not  so  good.  The  latter  is  rather  ineffective 
when  the  carbon  deposit  is  heavy. 

PACKING  WATER  PUMP  GLANDS.— The  water  pump  glands 
should  be  packed  with  a  good  grade  of  waterproof  asbestos  or  com- 
pounded packing.  If  loose  twisted  asbestos  rope  is  available  untwist 
one  strand,  soak  it  thoroughly  with  cylinder  oil,  and  cover  with  as 
much  fine  graphite  as  it  will  retain.  Always  coil  the  packing  round 
the  shaft  in  the  direction  the  packing  nut  turns  when  tightened  so 
it  will  not  tend  to  unwind  when  the  packing  nut  is  screwed  on.  The 
gland  nuts  should  not  be  tightened  any  more  than  is  necessary  to 
prevent  the  leakage  of  water. 

CLEANING  THE  COOLING  SYSTEM.— The  cooling  system 
should  be  flushed  with  a  stream  of  warm  water  (if  possible)  under 
pressure  by  forcing  it  through  the  system  in  the  reverse  direction  to 
which  the  water  flows  when  the  engine  is  operating.  To  accom- 
plish this  disconnect  the  radiator  at  the  lower  connection  and  insert 
a  hose  so  the  water  is  forced  in  at  the  bottom  of  the  radiator.  This 
should  remove  all  loose  dirt  and  sediment.  In  case  there  is  a  plug 
in  the  front  of  the  radiator  it  may  be  removed  and  the  water  forced 


322  MOTOR  VEHICLES  AND  THEIR  ENGINES 

in  at  this  point.  In  this  case  the  lower  hose  connection  to  the  radiator 
must  be  plugged. 

After  the  engine  has  been  used  some  time  and  the  cooling  system 
refilled  a  number  of  times,  probably  with  all  kinds  of  dirty  water,  a 
deposit  will  form  on  the  inside  surfaces  of  the  entire  cooling  system. 
This  prevents  proper  cooling  of  the  cylinders  and  of  the  water  in  the 
radiator.  To  remove  this  scale  dissolve  six  pounds  of  washing  soda 
in  five  gallons  of  boiling  water  and  pour  this  into  the  radiator  leaving 
it  in  the  system  while  the  car  operates  for  a  day.  Then  drain  out 
and  flush  the  cooling  system  with  clean  water  being  careful  to  refill 
it  with  clean  water.  In  addition  it  is  necessary  to  drain  the  radiator 
and  refill  with  fresh  water  at  frequent  intervals. 

FUEL  FEED  SYSTEM. — Gasoline  should  be  strained  before  it 
is  put  into  the  tank.  A  wire  gauze  or  chamois  strainer  can  be  used 
in  the  funnel  when  pouring  the  gasoline  in  the  tank.  In  case  chamois 
is  used  be  sure  to  keep  the  funnel  in  contact  with  the  tank  to  prevent 
the.  generation  of  dangerous  static  electricity. 

To  prevent  water  from  accumulating  the  sediment  trap  when 
provided  and  the  carburetor  should  be  drained  frequently.  This  is 
particularly  important  in  winter  as  the  water  may  freeze  and  stop 
up  the  gasoline  line.  The  carburetor  strainer  should  be  removed 
frequently  and  cleaned.  In  most  carburetors  this  is  accomplished 
by  loosening  a  union  at  the  bottom  of  the  carburetor  on  the  feed  line 
after  which  the  carburetor  may  be  removed.  In  unscrewing  the 
union  on  the  feed  line  be  careful  not  to  unscrew  the  whole  union 
fitting  and  twist  the  gasoline  line.  Also  be  sure  not  to  cross  the 
threads  in  screwing  the  union  back  on. 

The  joints  in  the  air  intake  manifold  should  be  examined  to  see 
that  there  are  no  leaks  as  they  are  frequently  the  cause  of  missing  in 
the  engine.  When  the  engine  is  running  these  leaks  may  be  detected 
by  putting  oil  on  the  suspected  spot  which  will  be  drawn  into  the 
manifold  if  there  is  a  leak.  Shellacking  the  joints  will  stop  this 
trouble  but  when  used  at  the  joints  above  the  governor  shellac 
should  be  applied  very  sparingly  as  it  may  flow  down  into  the 
governor  and  interfere  with  its  action.  Blotting  paper  without 
shellac  may  be  used  for  gaskets  at  these  joints. 

If  on  inspection  it  is  found  that  the  carburetor  is  flooding  with 
the  truck  standing  on  level  ground  the  cause  may  be  dirt  under  the 
float  needle  valve  or  a  leaky  valve.  The  small  cap  on  top  of  the 
float  chamber  should  be  removed  exposing  the  top  of  the  needle  valve 
stem  which  if  lifted  or  turned  may  release  the  dirt  causing  the  leak. 
If  the  leak  is  due  to  a  leaky  valve  a  few  light  taps  on  the  top  of  the 
valve  stem  may. cause  it  to  seat  properly.  Never  use  grinding  com- 


CARE  AND  ADJUSTMENT  323 

pound  on  this  valve  as  not  only  the  valve  but  also  the  seat  might 
be  ruined.  Further  details  as  to  care  of  the  carburetor  and  the 
methods  of  making  adjustments  will  be  found  in  the  chapters  on 
carburetors. 

WIRING. — All  wiring  of  the  starting,  lighting,  and  ignition 
systems  which  is  exposed  should  be  inspected  regularly  to  see  that  it 
is  not  chafed  or  rubbed  so  as  to  expose  the  bare  wire  and  cause  a 
ground.  The  wires  may  also  be  broken  inside  the  insulation  without 
giving  any  indication  on  the  outside.  This  is  most  apt  to  happen 
where  the  wire  takes  a  sudden  bend  or  vibrates  excessively.  Loose 
connections  should  be  tightened  and  where  a  wire  is  made  fast  to  a 
terminal  it  should  be  soldered.  A  grounded  primary  wire  on  a  Ford 
car  may  be  detected  by  the  constant  buzzing  of  the  vibrator  on  the 
corresponding  coil.  The  car  should  not  be  cranked  in  this  condition 
as  it  is  very  apt  to  kick  back. 

SPARK  PLUGS. — These  should  be  examined  frequently  to  see  if 
they  are  badly  carbonized,  porcelains  broken,  and  if  the  points  are 
improperly  adjusted  or  in  good  condition.  In  removing  plugs  care 
should  be  taken  not  to  allow  the  wrench  to  slip  and  break  the  porce- 
lain of  the  plug  being  removed  or  of  the  adjacent  one.  This  may  be 
avoided  by  never  using  a  worn  or  incorrect  sized  wrench  for  this  pur- 
pose and  by  always  starting  with  the  right  hand  plug  when  removing 
or  replacing  them.  Plugs  when  removed  may  be  cleaned  with  gaso- 
line. If  the  plug  is  demountable  the  porcelain  may  be  removed  and 
the  carbon  cleaned  off  with  an  old  tooth  brush  and  gasoline.  If  it 
is  impossible  to  remove  the  porcelain  the  plug  is  harder  to  clean  and 
the  carbon  may  be  scraped  off  the  metal  parts  after  being  softened 
with  gasoline.  A  knife  or  other  sharp  tool  may  be  used  but  care  must 
be  taken  not  to  scratch  the  glazed  surface  of  the  porcelain  as  this 
will  cause  it  to  become  oil  soaked  and  the  carbon  will  form  readily 
on  its  surface. 

The  gap  between  the  points  of  the  plug  should  be  between  1/32*' 
and  l/to>  With  battery  ignition,  or  on  the  Ford,  the  gap  may  be 
larger  than  with  high  tension  magneto  ignition.  Most  manufac- 
turers of  magnetos  and  ignition  systems  furnish  with  their  apparatus 
a  wrench  or  screwdriver  with  a  gauge  attached  of  the  proper  thick- 
ness so  that  it  will  just  slip  between  the  points  of  the  plug  when 
properly  adjusted.  As  a  substitute  gauge  for  battery  ignition  a  worn 
dime  may  be  used  but  for  magneto  ignition  the  gap  should  be  con- 
siderably smaller.  This  gap  should  be  inspected  frequently  as  the 
points  may  pit  or  wear  away  causing  the  gap  to  become  too  wide. 
This  will  make  it  difficult  to  start  the  engine  and  may  cause  the  plug 
to  miss  fire  at  low  speeds  or  when  pulling  hard  or  accelerating. 


324  MOTOR  VEHICLES  AND  THEIR  ENGINES 

The  plug  should  be  examined  carefully  in  case  it  does  not  fire  to 
see  if  a  porcelain  is  cracked  for  this  would  cause  the  plug  to  become 
short-circuited.  The  crack  may  be  a  fine  line  crack  which  is  rather 
difficult  to  detect.  In  replacing  bad  plugs  be  careful  to  get  the  proper 
type  of  plug.  Not  only  must  the  proper  thread  be  used  but  the  plug 
should  also  have  the  proper  length  as  previously  explained.  When 
inserting  a  half -inch  plug  be  careful  not  to  screw  it  too  tightly  into  a 
hot  engine  for  when  it  reaches  the  same  temperature  as  the  engine  it 
may  be  difficult  to  remove  the  plug. 

DISTRIBUTOR. — The  distributor  cover  on  a  magneto  or  battery 
system  should  be  removed  regularly  to  examine  the  brushes  or  con- 
tacts. The  distributor  plate  should  be  cleaned  with  a  cloth  dipped 
in  gasoline.  After  cleaning  the  distributor  the  rotor  or  brush  track 
should  be  given  a  very  fine  application  of  vaseline.  If  the  distributor 
has  brushes  be  very  careful  not  to  lose  or  damage  them  in  removing 
the  cover.  If  the  car  is  equipped  with  a  timer  and  multi-unit  coil 
the  timer  should  be  cleaned  at  frequent  intervals  with  a  cloth  wet 
with  gasoline. 

INTERRUPTERS.— Another  important  part  of  the  magneto  or 
ignition  system  is  the  interrupter.  The  interrupter  lever  should  be 
examined  to  see  that  it  is  free  to  move  and  the  gap  between  the 
interrupter  points  should  be  inspected.  To  check  the  adjustment 
of  these  points  set  the  interrupter  lever  on  the  center  of  the  cam 
which  gives  the  maximum  opening  of  the  points.  Then  check  the  gap 
between  them  with  the  gauge  supplied  for  that  purpose  on  the  mag- 
neto wrench  or  screw  driver.  If  this  should  not  be  available  set  the 
points  from  0.015"  to  0.020"  apart  using  a  post  card  to  gauge  the  dis- 
tance. This  gap  should  be  checked  on  each  cam  particularly  on  those 
magnetos  which  have  the  cams  on  the  interrupter  lever  housing.  If 
the  cams  are  worn  or  the  housing  is  worn  or  distorted  the  gaps  will  be 
unequal.  This  may  be  corrected  by  shimming  under  the  cam  which 
gives  the  least  opening.  This  work  as  well  as  the  filing  of  the  breaker 
points  should  be  done  only  by  experienced  mechanics.  If  the  breaker 
points  are  pitted  or  do  not  make  a  good  contact  it  will  be  necessary  to 
dress  the  points  with  a  fine  file  until  the  surfaces  are  smooth  and  make 
proper  contact.  The  gap  should  be  properly  adjusted  after  the 
points  are  filed.  The  points  of  a  vibrator  need  the  same  attention, 
the  proper  gap  being  about  l/szlf  with  the  spring  held  all  the  way  down. 

LUBRICATION  OF  MAGNETO.— In  lubricating  a  magneto  fol- 
low instructions  given  as  proper  lubrication  is  one  of  the  essential 
points  for  satisfactory  operation  of  a  magneto  or  timer-distributor. 
Too  much  oil  is  as  bad  as  too  little,  since  it  is  apt  to  get  on  the  windings 
or  breaker  points. 


CARE  AND  ADJUSTMENT  325 

IGNITION  TIMING.— To  time  the  magneto  first  bring  number 
one  piston  (the  one  nearest  the  radiator)  to  top  dead  center  on  com- 
pression stroke.  This  may  be  done  by  opening  the  priming  cocks  on 
the  other  cylinders  and  turning  the  engine  until  compression  is  felt. 
The  piston  is  then  coming  up  on  compression  stroke  and  if  the  fly 
wheel  is  exposed  it  may  be  brought  to  top  dead  center  by  checking  the 
marks  on  the  flywheel.  If  the  flywheel  is  not  exposed  an  approxi- 
mate method  may  be  used  which  is  close  enough  to  check  the  setting 
of  the  magneto  and  determine  whether  faulty  timing  is  the  cause  of 
trouble.  Insert  a  wire  or  stick  through  the  spark  plug  hole  and  turn 
the  engine  until  this  wire  stops  rising.  If  this  is  carefully  done  the 
position  of  top  dead  center  can  be  located  to  within  about  five  degrees. 
If  it  is  necessary  to  connect  up  the  magneto  by  this  method,  it  is  best 
to  continue  turning  the  engine  after  the  piston  reaches  the  top  of  its 
stroke  until  it  just  starts  to  move  downward  again.  This  will  prevent 
timing  the  magneto  too  early  which  might  cause  the  engine  to  kick 
back  when  being  cranked.  However,  the  magneto  should  never  be 
set  by  this  approximate  method  except  in  case  of  an  emergency. 

With  the  engine  set  at  top  dead  center  the  magneto  should  be 
turned  until  the  distributor  contact  is  opposite  the  brush  to  number 
one  cylinder.  Then  set  so  that  the  contact  points  are  just  about  to 
open  with  the  spark  retarded.  The  magneto  should  be  turned  in  the 
direction  of  rotation  in  making  this  adjustment.  Some  magnetos  are 
marked  on  the  distributor  plate  with  a  line  and  an  L  or  R  depending 
on  the  direction  of  rotation  of  the  magneto.  This  mark  is  so  located 
that  it  comes  opposite  a  marking  pin  just  as  the  contact  points  open, 
with  the  distributor  contact  opposite  the  lead  to  number  one  cylinder. 
This  simplifies  the  checking  of  the  timing  considerably  when  the 
breaker  box  is  inaccessible.  After  timing  the  magneto  to  the  engine 
connect  the  coupling  between  them.  After  the  two  are  connected 
check  the  setting  to  make  sure  nothing  was  displaced  while  tightening 
the  coupling.  Observe  which  way  the  distributor  rotates  and  con- 
nect the  leads  from  the  distributor  so  that  each  cylinder  receives  the 
spark  in  the  proper  firing  order. 

A  timer-distributor  on  a  battery  ignition  system  is  timed  in  prac- 
tically the  same  manner.  Bring  number  one  piston  to  top  dead 
center  on  compression  stroke  as  before,  but  continue  to  turn  the  engine 
until  the  exhaust  valve  on  the  other  cylinder  which  is  on  top  center 
(number  4  on  a  four  cylinder  engine  or  number  6  on  a  six  cylinder 
engine)  just  closes.  Loosen  the  breaker  cam  adjusting  screw  on  the 
vertical  shaft  and  set  the  breaker  points  so  they  just  start  to  open  with 
the  spark  fully  retarded.  The  rotor  must  also  be  in  such  a  position 
that  the  distributor  makes  contact  with  the  segment  for  number  one 


326  MOTOR  VEHICLES  AND  THEIR  ENGINES 

cylinder.  The  breaker  cam  must  be  set  carefully  so  that  the  points 
will  open  and  close  as  the  slack  in  the  distributor  gears  is  taken  up 
first  in  one  direction  and  then  in  the  other.  Tighten  the  adjusting 
screw  and  after  replacing  the  rotor  connect  the  leads  to  the  plugs  as 
in  the  case  of  the  magneto. 

To  time  the  " commutator"  on  the  Ford  bring  number  one  piston 
to  top  dead  center  on  compression  stroke  as  before.  As  the  cylinder 
head  must  be  removed  to  properly  time  the  "commutator"  the  meth- 
od given  above  for  determining  firing  position  is  not  applicable.  The 
simplest  way  to  determine  this  position  is  by  watching  the  exhaust 
valve  of  number  four  cylinder,  for  as  it  closes  piston  number  one  will 
be  at  top  dead  center  on  compression  stroke.  After  reaching  top  dead 
center  continue  to  turn  the  engine  until  the  piston  has  traveled  y% 
on  the  downward  stroke.  Set  the  " commutator"  in  the  full  retarded 
position  and  place  the  roller  so  that  it  is  just  starting  to  make  contact 
with  number  one  segment.  Connect  up  the  primary  wires  so  that  the 
spark  occurs  in  the  proper  cylinder.  It  must  be  remembered  that  the 
firing  order  of  the  Ford  is  1-2-4-3,  which  is  different  from  most  four- 
cylinder  engines. 

CLUTCH  ADJUSTMENTS.— If  the  clutch  slips  before  adjusting 
the  clutch  spring  make  sure  that  the  clutch  pedal  is  not  striking  the 
floor  boards  or  that  some  other  obstruction  is  not  preventing  the 
clutch. spring  from  forcing  the  friction  surfaces  together.  When  it  is 
necessary  to  adjust  the  spring  tension  this  is  accomplished  by  moving 
the  adjusting  nut  provided  for  that  purpose.  After  the  adjustment 
has  been  made  make  sure  the  nut  is  securely  locked  in  place. 

If  the  clutch  has  a  clutch  brake  see  that  it  is  properly  adjusted. 
This  brake  should  be  so  adjusted  that  it  takes  effect  only  at  the  ex- 
treme outward  position  of  the  clutch  pedal.  Common  clutch  troubles 
and  their  remedies  are  covered  in  chapter  23. 

WHEEL  ALIGNMENT.— The  method  of  aligning  the  wheels 
depends  upon  whether  the  vehicle  is  steered  by  two  or  all  four  wheels. 
On  a  two- wheel  steered  vehicle  a  simple  method  is  as  follows :  Turn 
the  steering  wheel  until  the  right  front  wheel  is  in  line  with  the  right- 
rear  wheel.  To  determine  this  a  piece  of  string  may  be  stretched 
along  the  outside  of  the  right  wheels  touching  both  the  front  and  rear 
edges  of  both  wheels  lightly  or  they  may  be  aligned  by  the  eye.  With 
the  wheels  set  in  this  position  test  the  front  wheels  for  " gather"  or 
"toeing  in"  by  sighting  along  the  inner  edge  of  the  left  front  wheel. 
If  properly  adjusted  an  inch  to  an  inch  and  a  half  of  the  rear  wheel  will 
be  visible  which  is  approximately  one  quarter  of  an  inch  "gather  " 
If  more  or  less  of  the  rear  wheel  is  visible  the  tie  rod  should  be 
adjusted. 


CARE  AND  ADJUSTMENT  327 

With  a  four-wheel  steered  vehicle  both  sets  of  wheels  should  be 
set  to  "toe  in"  and  the  simplest  way  is  to  measure  the  amount  of 
difference  in  distance  between  the  edges  of  the  front  and  rear  of  the 
wheels  with  a  stick  when  they  are  set  approximately  parallel  with  the 
frame. 

To  determine  the  amount  of  "gather"  by  these  methods  it  is 
necessary  for  the  wheels  to  run  true.  This  may  be  determined  by 
jacking  them  up  one  at  a  time  and  spinning  them.  If  not  true  a 
wooden  wheel  may  be  turned  up  as  follows:  Hold  a  piece  of  chalk 
against  the  side  of  the  spinning  wheel  to  indicate  where  the  wheel  is 
distorted.  Cardboard  shims  may  now  be  placed  between  the  spokes 
and  inner  hup  plate  where  necessary  to  make  the  wheel  run  true. 
When  demountable  rims  are  used  do  not  confuse  the  improper  setting 
of  the  rim  bolts  causing  the  tire  to  run  out  of  true  with  a  wheel  out  of 
true.  Both  should  be  avoided  as  they  cause  undue  wear  on  the  tires. 

STEERING  GEAR.— While  the  wheel  is  jacked  up  it  should  be 
tested  for  play  in  the  wheel  bearings,  steering  knuckle,  and  also  tie 
rod  or  the  drag  link.  This  play  should  be  taken  up  at  once  if  pos- 
sible. Lost  motion  in  the  steering  gear  should  be  taken  up  as  soon 
as  it  is  discovered  if  an  adjustment  for  this  purpose  is  provided.  In 
some  constructions  the  steering  arm  is  actuated  by  a  short  shaft  with 
a  square  end  on  which  the  arm  fits.  Lost  motion  often  occurs  at 
this  point  and  the  steering  arm  should  be  inspected  and  clamped 
tightly  on  the  shaft  if  any  movement  occurs  between  them. 

BRAKE  ADJUSTMENT.— Before  adjusting  the  brakes  make 
sure  that  the  cause  of  their  failure  to  work  is  not  due  to  oil  or  grease 
on  the  linings.  If  this  is  the  case  make  sure  that  the  grease  or  oil  is 
thoroughly  removed  with  kerosene.  It  will  probably  be  necessary 
in  case  of  a  wheel  brake  to  remove  the  wheel  to  do  this  properly  and 
to  remove  the  brake  band  in  case  of  a  transmission  brake.  If  the 
brake  band  is  clean  and  does  not  need  replacement  it  is  ready  for 
adjustment.  In  a  transmission  brake  there  are  usually  two  places 
for  adjustment,  at  the  brake  adjusting  screw  to  allow  for  wear  of  the 
brake  band  and  on  the  brake  rods  to  adjust  the  position  of  the  brake 
pedal.  Wheel  brakes  usually  have  another  adjustment  to  obtain 
equal  pull  from  the  equalizer. 

In  adjusting  any  brake  be  sure  to  observe  the  following  points: 

First,  make  sure  that  the  brake  lining  clears  the  drum  all  around 
by  a  small  and  approximately  equal  amount  with  the  brake  pedal 
in  the  fully  released  position.  This  adjustment  can  usually  be  made 
with  the  adjusting  screws  on  the  brake  and  by  the  brake  band 
supports. 

Second,  with  the  pedal  approximately  one  third  depressed  the  lin- 


328  MOTOR  VEHICLES  AND  THEIR  ENGINES 

ing  should  make  uniform  contact  throughout  its  entire  surface  with 
the  brake  drum.  This  may  be  accomplished  by  adjusting  the  brake 
rods  and  the  brake  adjusting  screws  making  sure  in  case  of  wheel 
brakes  that  all  take  hold  at  the  same  time. 

If  these  adjustments  are  properly  made  the  service  brake  should 
lock  the  wheels  with  the  car  running  light  when  the  brake  pedal  is 
two-thirds  depressed.  If  the  brakes  grab  or  screech  a  few  drops  of 
castor  oil  or  light  mineral  oil  may  stop  the  trouble. 

SPRINGS. — In  addition  to  spring  lubrication  it  is  important 
that  the  spring  clips  be  properly  adjusted.  The  clips  themselves 
should  be  examined  to  see  that  they  are  not  broken  and  that  they  fit 
snugly  to  the  leaves.  The  bolts  should  be  kept  tight  but  not  so  tight 
as  to  cause  the  tops  of  the  clips,  to  be  bent  in  over  the  top  of  the  spring 
pinching  it  and  causing  either  the  spring  or  clip  to  break.  The  spring 
saddle  bolts  should  be  inspected  frequently  to  see  that  they  are  not 
loose. 


CHAPTER  XXXII 


CARE  AND  ADJUSTMENT  TABLES 

A  systematic  method  of  attention  at  definite  intervals  is  necessary 
to  keep  motor  vehicles  operating  satisfactorily.  Lack  of  attention 
does  not  show  immediately,  often  resulting  in  certain  parts  being 
neglected  when  unsystematic  methods  are  used. 

Lubrication,  adjustment,  and  inspection  should  be  done  at  regular 
intervals  rather  than  on  a  mileage  basis.  Particularly  when  the 
apparatus  is  in  continuous  use,  such  as  trucks  or  cars  used  for  com- 
mercial purposes.  However,  common  sense  must  be  used  to  prevent 
under  or  over  lubrication  when  a  vehicle  is  used  more  than  usual  or 
very  little.  In  this  case  it  is  best  to  go  back  to  the  mileage  basis. 
It  is  a  popular  misconception,  particularly  among  chauffeurs,  that 
lubrication  is  over-emphasized.  To  illustrate  the  method  of  making 
systematic  inspection,  on  the  basis  of  daily,  weekly,  and  monthly 
attention,  a  table  is  worked  out  for  the  Dodge  and  Ford  cars,  as  well 
as  F.  W.  D.  and  Nash  trucks. 

A  very  important  point  in  the  care  of  a  car  and  one  strongly 
emphasized  in  the  French  army  is  the  inspection  of  motor  vehicles  on 
the  road.  During  the  first  hour's  running  most  of  the  troubles  which 
will  occur  have  started  to  develop  and  an  inspection  for  leaks  and 
loose  parts  as  outlined  in  Table  I  made  at  this  time  may  save  serious 
trouble  later.  A  few  moments  spent  in  this  manner  reduces  to  a 
minimum  the  loss  of  time  which  occurs  due  to  break-downs  and  also 
keeps  down  the  repair  expenses.  This  will  be  particularly  true  of 
trucks  when  the  apparatus  is  used  continually. 

If  all  garages  or  truck  and  car  owners  would  make  out  a  chart  as 
shown  in  Table  6  for  each  particular  car,  they  could  keep  an  exact 
record  of  the  oil  and  gasoline  used  and  have  a  record  of  the  systematic 
method  used  to  keep  the  car  in  proper  running  order.  The  only 
addition  needed  to  make  this  table  complete  is  to  consult  the  man- 
ufacturers lubrication  chart  and  list  separately  each  part  to  be 
lubricated  just  as  is  done  in  the  table  for  the  other  cars  and  trucks. 
Uses  the  same  checking  system  as  used  for  the  care  of  the  car. 

329 


330  MOTOR  VEHICLES  AND  THEIR  ENGINES 

TABLE  1 
ROAD  INSPECTION  FOR  TRUCKS 

1  Before  leaving  the  garage  in  the  morning  the  oil  level  in 
the  crank  case  should  be  examined,  the  radiator  filled  with 
soft  water,  and  the  gasoline  tank  examined  to  see  if  there  is 
sufficient  gasoline.  Run  the  engine  until  warm  before  starting 
the  car,  meanwhile  looking  for  gasoline,  oil,  or  water  leaks. 
It  is  especially  important  to  have  the  engine  warm  before 
starting  the  car  in  cold  weather. 

2.  As  soon  as  the  car  is  started  test  the  steering  mechanism  and 

brakes  for  proper  operation,  and  correct  any  troubles.     Listen 
carefully  for  unusual  sounds  and  locate  their  causes. 

3.  After  running  for  about  an  hour  stop  the  car  and  examine  as 

follows : 

A.  Let  the  engine  idle  and  lift  hood. 

Inspect  fan  belt  for  tension  and  bearings  for  overheating. 
Examine  engine  for  compression  leaks  around  valve  caps  and 

plugs. 

Look  for  air  leaks  around  carburetor  and  intake  manifold. 
Feel  pipe  at  water  pump  to  see  if  pump  is  operating  properly. 
Examine  magneto  and  cables  for  loose  connections. 
If  oil  pump  can  be  tested  by  opening  pet  cocks  do  so. 

B.  Feel  brake  drums  to  see  if  they  are  hot  due  to  dragging 

brakes. 

Inspect  springs  for  loose  clips  and  shifted  or  broken  leaves. 
Note  any  leakage  of  oil  from  differential,  axles,  or  wheels. 
If  the  wheels  have  grease  plugs  examine  to  see  if  tight. 
Examine  hub  caps,  universal  joints,  housing,  and  grease  cup 

caps  to  see  if  secure. 

C.  Note  any  oil  leaks  from  transmission,  universal  joints,  or 

clutch  and  if  the  car  has  a  transmission  brake,  examine  for 
heat  due  to  brake  band  dragging. 

D.  Examine  ground  under  engine  for  oil  or  water  dropping 

from  leaks. 
If  engine  has  external  oil  pump  look  for  oil  leaks  at  pump 

and  tubing. 
Have  some  one  turn  steering  wheel  and  examine  all  steering 

mechanism,  particularly  drag  links  and  tie  rods  for  loose 

connections. 


CARE  AND  ADJUSTMENT  TABLES  331 

4.  This  inspection  should  be  very  carefully  made  if  the  car  has  just 

returned  from  the  repair  shop,  as  defects  which  may  not  be 
noticed  in  the  shop  will  develop  when  the  engine  becomes 
thoroughly  "  warmed  up." 

5.  On  returning  to  the  garage,  fill  with  gasoline  and  carry  out  the 

daily  attention  prescribed  herein  for  the  particular  car. 
In  cold  weather  drain  all  water  from  the  cooling  system  and 
suspend  a  tag  marked  " Drained"  from  the  filler  cap.     This 
must  always  be  done  when  the  system  is  drained. 

TABLE  2 

DODGE  CARS 

DAILY  ATTENTION 

A.  The  oil  level  indicator  rod  should  be  examined  and  enough 

medium  grade  cylinder  oil  should  be  added  to  bring  the  top 
of  the  rod  to  within  Y^'  of  the  waterjackets.  The  oil  should 
never  be  allowed  to  fall  so  low  that  the  top  of  the  rod  is 
within  }/<£  of  the  lower  casting. 

B.  Turn  the  following  grease  cups  and  refill  when  necessary  with 

cup  grease: 

1.  Clutch  release  grease  cup. 

2.  Engine  fan  shaft  grease  cup. 

3.  Steering  gear  tie  rod  grease  cups. 

4.  Spring  bolt  grease  cups. 

5.  Steering  gear  worm  wheel  shaft  grease  cup. 

6.  Steering  gear  drag  link  grease  cups. 

C.  Turn  up  water  pump  grease  cups  and  refill  every  100  miles. 

D.  Examine  tires  and  see  that  they  are  properly  inflated. 

WEEKLY  ATTENTION 

A.  With  cup  grease, 

1.  Pack  the  steering  gear  drag  link. 

2.  Remove  plug  and  fill  universal  joint  housing. 

B.  With  cylinder  oil  (medium)  fill, 

1.  Rear  spring  seat  strap  oil  cups. 

2.  Brake  operating  shaft  oilers. 

3.  Steering  knuckle  bolt  oil  cups. 


332  MOTOR  VEHICLES  AND  THEIR  ENGINES 

C.  Put  a  few  drops  of  cylinder  oil  in, 

1.  Steering  wheel  oil  hole. 

2.  Brake  equalizer  clevis  pins. 

3.  All  brake  pull  rods  and  yoke  clevis  pins. 

4.  Brake  operating  shaft  oilers. 

5.  Hand  brake  lever  latch  rod  and  button. 

6.  Accelerator  pedal  shaft  brackets. 

7.  Spark  and  throttle  rod  ball  and  socket  joints. 

8.  Brake  pedal. 

9.  Clutch  pedal  shaft  oil  holes. 

D.  Clean  thoroughly  engine,  running  gear,  and  body,  carefully 

wiping  off  all  excess  oil  and  grease. 

E.  Test  the  specific  gravity  in  each  cell  of  the  storage  battery  with 

a  hydrometer.     If  the  specific  gravity  is  below  1.200  the  bat- 
tery needs  attention. 

After  testing  fill  with  distilled  water  until  the  liquid  stands 
y£  above  the  plates.  Do  not  fill  too  full  and  do  not  add  any- 
thing but  distilled  water. 

F.  Inspect  engine. 

1.  See  that  wiring  connections  are  tight  and  clean. 

2.  Remove,  clean,  and  adjust  the  spark  plugs. 

3.  Clean  the  distributor  plate  with  a  dry  rag  and  apply  a  very 

small  amount  of  vaseline  to  the  distributor  track  (250 
miles). 

4.  While  engine  is  running  inspect  water  pump  packing  and 

grease  cups  for  leaks. 

5.  Listen  to  the  engine  when  running  for  loose  bearings  or  noisy 

timing  gears. 

6.  Make  sure  that  the  oil  purnp  case  cover  is  securely  attached 

and  that  there  is  no  leak  through  the  gasket. 

7.  See  that  the  oil  gage  registers  properly  when  the  engine  is 

running. 

8.  Test  for  compression  in  each  cylinder,  by  turning  the  engine 

over  by  hand,  and  locate  cause  if  compression  is  weak. 

9.  Inject  a  tablespoonful  of  kerosene  in  each  cylinder  through 

the  pet  cocks  while  the  engine  is  hot  and  let  it  stand  over 
night'to  loosen  the  carbon  in  the  cylinder. 


CARE  AND  ADJUSTMENT  TABLES  333 

G.    Inspect  cooling  system. 

1.  Look  for  leaks  in  radiator  and  hose. 

2.  See  that  the  fan  belt  rides  evenly  and  that  it  has  the  proper 

tension. 

3.  Drain  radiator  and  refill  with  fresh  water. 

H.    Inspect  gasoline  line  and  carburetor  for  leaks  and  clean  the 
strainer. 

I.  Examine  brake  bands  to  see  that  they  are  not  dragging  or  bind- 
ing or  that  oil  is  not  leaking  on  them  from  the  rear  axle.  Wipe 
off  the  brake  drums  with  kerosene  if  they  are  oily. 

J.  Test  front  wheels  for  alignment  and  see  if  rear  wheels  track  front 
wheels. 

K.    Inspect  springs  to  see  that  spring  clips  are  tight  and  that  the 
leaves  have  not  shifted. 

L.    Examine  tires  for  cuts,  stone  bruising,  sand  blisters,  etc.     Test 

air  pressure  with  tire  gauge. 

M.    Note  during  week  all  body  squeeks,  rattles,  etc.,  and  remedy  by 
tightening  bolts.     Inspect  car  thoroughly  for  loose  bolts,  etc. 


MONTHLY  ATTENTION 

A.  Remove  oil  strainer  from  breather  pipe  and  clean  and  drain  oil 

from  crank  case  (1000  miles). 

Remove  blow-out  plug  at  rear  end  of  distributing  oil  tube  in 
the  interior  of  the  crank  case  and  disconnect  oil  tube  at  the 
pump.  Blow  through  this  pipe  to  clean  it  out.  Every  other 
month  remove  oil  strainer  at  bottom  of  crank  case  and  clean 
(2000  miles).  Before  replacing  strainer  wash  out  pan  with 
kerosene  poured  in  through  the  breather  tube.  Turn  engine 
over  rapidly  by  hand  or  starter  to  remove  remaining  kerosene. 
Replace  strainer,  reconnect  oil  tube,  and  refill  crank  case  with 
six  quarts  of  cylinder  oil  (medium).  When  engine  is  running 
examine  exposed  oil  pipes  for  leaks. 

B.  Make  sure  that  the  valves  have  the  proper  clearance  (0.004") 

and  set  those  that  have  not  by  adjusting  the  valve  tappet 
adjusting  screws. 

C.  The  wiring  of  the  starting,  lighting,  and  ignition  systems  should 

be  inspected  carefully  to  see  that  all  terminal  connections  are 
tight  and  that  the  insulation  has  not  been  chafed  or  rubbed 
off  to  cause  a  short  circuit.  Put  four  or  five  drops  of  cylinder 
oil  (medium)  in  distributor  bearing  oil  well. 


334  MOTOR  VEHICLES  AND  THEIR  ENGINES 

D.  Remove  the  plug  in  the  lower  end  of  the  steering  gear  housing 

and  fill  with  cup  grease.  Also  put  several  drops  of  cylinder 
oil  (medium)  in  the  spring  oiler  at  the  top  of  the  column. 

E.  Inspect  level  of  oil  in  the  transmission  which  should  be  kept 

up  to  the  idler  gear.  Every  three  months  (2500  miles)  drain 
the  transmission,  wash  with  kerosene,  and  refill  with  five  pints 
of  transmission  oil. 

F.  Remove  clutch  inspection  plate  and  examine  clutch  release 

grease  tube  and  clutch  operation  and  alignment. 

G.  Remove  upper  and  lower  plug  from  differential  housing  and  fill 

with  steam  cylinder  or  transmission  oil  until  it  runs  out  of 
lower  plug.  Drain,  clean  with  kerosene  oil,  and  refill  with 
oil  every  three  months. 

H.    Remove  wheels,  clean  bearings,  and  repack  with  grease  every 
two  months,  packing  the  front  wheels  one  month  and  the 
rear  wheels  the  next. 
I.    Lubricate  between  the  spring  leaves  every  two  months  with 

grease  and  graphite. 

J.    Examine  the  chassis  for  loose  bolts  or  other  loose  parts,  par- 
ticularly in  the  following  places : 

1.  Universal  joint  ring  and  yokes. 

2.  Transmission  arm  bolts. 

3.  Front  motor  support  bolts. 

4.  Oil  pan  and  transmission  bolts. 


TABLE  3 

FORD  CARS 

DAILY  ATTENTION 

A.  The  crank  case  should  be  filled  with  cylinder  oil  (medium)  until 

it  runs  out  of  the  upper  pet  cock.     The  oil  must  at  all  times 
be  kept  above  the  level  of  the  lower  pet  cock. 

B.  Turn  the  following  grease  cups  and  refill  when  necessary  with 

cup  grease: 

1.  Fan  grease  cup,  several  turns. 

2.  Rear  axle  roller  bearing  grease  cup,  all  the  way  down. 

C.  Put  a  few  drops  of  cylinder  oil   (medium)   in   the  following 

places : 

1.  Commutator. 

2.  Front  and  rear  spring  hangers. 


CARE  AND  ADJUSTMENT  TABLES  335 

3.  Spindle  arm  and  spindle  body  bolts. 

4.  Ball  joints  on  steering  connecting  rod. 
D.    Inspect  and  test, 

1.  Brakes  and  adjust  if  necessary. 

2.  Tires  for  proper  inflation. 

3.  Tighten  loose  nuts  and  wiring  terminals. 

4.  Springs  for  breakage. 

5.  Wheel  alignment  and  all  steering  connections. 


WEEKLY  ATTENTION 

A.  Examine  car  for  gasoline,  water,  or  oil  leaks. 

B.  Wash  and  polish  car. 

C.  Clean  the  outside  of  engine  and  crank  case  thoroughly. 

D.  Wipe  off  any  oil  or  grease  on  fan  belt  and  adjust  or  replace  same 

if  necessary. 

E.  Jack  up  front  end  of  car  and  try  for  excessive  lateral  play  in 

wheels,  adjusting  the  bearings  when  necessary. 

F.  Test  alignment  of  front  wheels  and  adjust  if  necessary. 

G.  Inspect  steering  system  thoroughly. 
H.    Adjust  foot  pedals. 

I.    Equalize  and  adjust  emergency  brakes. 
J.    Tighten  all  loose  bolts. 

K.    Tighten  all  loose  connections  in  the  ignition  system. 
L.    Oil    the    following    parts   with   a    few    drops    of    cylinder    oil 
(medium) : 

1.  Starting  crank  handle. 

2.  Ball  and  socket  joints  on  spark  control  lever. 

3.  Hand  brake  lever  pawl  and  lift  handle. 

4.  Controller  shaft  brackets. 

5.  Speed  lever  on  controller  shaft. 

6.  Brake  rod  clevis  pins. 

7.  Brake  rod  supports. 

8.  Emergency  brake  shoe  cam  shafts. 

M.    Turn  the  following  grease  cups  and  refill  when  necessary  with 
cup  grease: 

1.  Steering  post  bracket  grease  cup,  two  turns. 

2.  Universal  ball  joint  grease  cup,  turn  down  and  refill  twice. 

3.  Drive'  shaft  housing  grease  cup,  front  end,  two  turns. 
N.    Examine  spark  plugs,  clean  and  adjust  gaps. 


336  MOTOR  VEHICLES  AND  THEIR  ENGINES 

0.  Fill  front  hub  caps  with  cup  grease. 

P.  Examine  tires  for  cuts  and  bruises  and  test  for  proper  inflation. 

Q.  Drain  carburetor  and  sediment  bulb  of  dirt  and  water. 


MONTHLY  ATTENTION 

A.  Drain  crank  case,  wash  with  kerosene,  and  refill  with  cylinder  oil 

(medium),  (1000  miles). 

B.  Clean  cooling  system  and  examine  and  repair  leaky  radiator, 

faulty  connections,  and  worn  out  hose. 

C.  Clean  gasoline  line. 

D.  Remove  and  clean  commutator  case. 

E.  Examine  commutator  roller  for  too  much  play  and  wires  for 

frayed  insulation. 

F.  Examine  coil  unit. 

G.  File  pitted  or  uneven  points  and  adjust  same  to  a  gap  of  }(&  an 

inch  when  springs  are  carefully  depressed. 
H.    Remove  and  clean  magneto  contact  plug  on  top  of  transmission 

cover  and  see  that  contact  points  are  at  the  end  of  the  coil 

spring  when  replacing  the  plug. 
I.    Test  for  poor  compression,  leaking  cylinder  head  gasket,  loose 

bearings,  and  carbon  in  the  cylinders. 

J.    Remove  the  steering  case  cover,  pack  the  case  with  cup  grease. 
K.    Inspect  ball  and  socket  joint  at  end  of  steering  connecting  rod 

and  eliminate  all  loose  motion  by  removing  and  filing  down 

faces  of  the  ball  socket  caps. 
L.    Jack  up  front  axle  and  examine  for  loose  spindle  arm  and  worn 

spindle  body  bushings. 
M.    Examine  spring  hanger  bushing,  front  and  rear,  and  replace  when 

necessary. 

N.    Remove  front  wheel,  examine  and  pack  bearings  with  grease. 

Inspect  stationary  and    adjusting    cones   before   replacing. 
O.    Remove  front  radius  rod  ball  cap  and  pack  with  grease. 
P.    Remove  rear  hub  cap  and  tighten  rear  hub  lock  nuts. 
Q.    Tighten  engine  bolts  to  frame. 
R.    Grease  springs  with  graphite  and   cup  grease  and  replace  the 

tie  bolts  when  necessary. 
S.    Tighten  spring  clip  nuts  which  hold  the  front  and  rear  spring 

to  cross  members  of  the  frame. 


CARE  AND  ADJUSTMENT  TABLES  337 

T.    Tighten  spring  retainer  clips. 
U.    Reline  transmission  bands  if  necessary. 
V.    Equalize  and  adjust  emergency  brake. 

W.    Remove  plug  in  rear  axle  and  fill  differential  housing  one-third 
full  of  non-fluid  transmission  lubricant  (1000  miles). 


TABLE  4 

F.  W.  D.  TRUCKS 
DAILY  ATTENTION 

A.  The  crank  case  should  be  filled  with  cylinder  oil  (medium) 

until  the  oil  just  runs  from  the  upper  pet  cock  on  the  crank 
case  with  engine  stopped  and  car  level.  Care  must  be  taken 
not  to  put  more  oil  than  is  just  necessary  to  bring  it  to  this 
level.  Do  not  depend  on  the  oil  gauge  to  tell  you  the  oil  level. 
Make  sure  the  pet  cocks  on  the  crank  case  are  not  plugged. 

B.  A  few  drops  of  cylinder  oil  (medium)  should  be  placed  on  each 

of  the  following  places : 

1.  Outer  starting  crank  bearing. 

2.  Inner  starting  crank  bearing. 

3.  Rocker  pin  bearing  on  fan  belt  bracket. 

4.  Radiator  support  bearings. 

5.  The  dogs  on  the  gear  shift  lever  and  gear  shift  lever  shaft 

and  bearings. 

6.  All  pins  on  gear  shift  rods  and  clutch  and  brake  rods. 

7.  Clutch  pedal  and  brake  pedal  bearings. 

8.  Foot  brake  bell  crank  bearings  and  on  pins  in  foot  brake 

mechanism. 

9.  Emergency  brake  equalizer  pins  and  slides. 

10.  Pins  on  emergency  brake  mechanism. 

11.  Spark  and  throttle  control  joints  and  bearings. 

12.  Plunger  on  horn. 

13.  Shaft  inside  upper  torque  rod  spring.     After  lubricating 

wipe  off  excess  oil. 

C.  Turn  the  following  grease  cups  and  when  necessary  fill  with 

cup  grease. 

1.  Fan  pulley  bearing,  several  turns. 

2.  Fan  belt  drive  shaft,  several  turns. 

3.  Front  spring  bolts,  one  turn. 

4.  Steering  knuckle,  four  turns. 


338  MOTOR  VEHICLES  AND  THEIR  ENGINES 

5.  Steering  arms,  one  turn. 

6.  Clutch  shifter  shaft  and  shifter,  several  turns. 

7.  Water  pump,  two  turns. 

8.  Torque  rod  and  arms,  one  turn. 

9.  Gear  shifter  and  jackshaft,  one  turn. 
10.  Rear  springs  bolts,  one  turn. 

D.    Turn  down  grease  cups  on  upper  propeller  shaft  universal  joints 
two  turns  every  other  day. 

F.  Clean,  trim,  and  fill  all  lamps  and  acetylene  generator. 

G.  Wipe  off  magneto  and  wiring. 


WEEKLY  ATTENTION 

A.  Clean  truck  thoroughly. 

B.  Thoroughly  clean  engine  and  engine  compartment. 

C.  Remove  spark  plugs,  clean  and  adjust  gaps,  and  replace;  inspect 

and  clean  wiring,  and  clean  distributor  plate  with  gasoline. 

D.  Run  the  engine,  watching  for   water  and   oil   leaks,   unusual 

sounds  and  loose  parts;  examine  for  air  leaks  around  inlet 
manifold  and  carburetor. 

E.  When  engine  is  hot,  stop  and  test  compression  by  turning  over 

by  hand. 

F.  While  the  engine  is  hot  inject  a  tablespoonful  of  kerosene  in  each 

cylinder  through  the  petcocks  and  let  stand  overnight  to 
loosen  the  carbon. 

G.  Turn  clutch  so  that  one  filling  plug  is  on  top.     Remove  plug  and 

turn  engine  J/£  revolution  until  next  plug  is  on  top.  Remove 
this  plug  and  add  a  mixture  of  cylinder  oil  (medium)  and 
kerosene  till  it  runs  out  of  the  lower  open  plug.  Replace  the 
plugs.  The  proportions  of  oil  and  kerosene  vary  from  two 
parts  kerosene  to  one  of  oil  in  cold  weather  to  one  part  kero- 
sene to  two  of  oil  in  hot  weather.  Inspect  clutch  pedal  to 
see  that  it  does  not  strike  floor  board  when  the  clutch  is 
engaged.  Adjust  clutch  brake  if  necessary. 

H.    Pack  lower  propeller  shaft  universal  joints  with  grease. 

I.    Tighten  bolts  on  alignment  joint. 

J.  Tighten  spring  clip  nuts  and  inspect  springs  for  shifted  or 
broken  spring  leaves. 

K.  Inspect  wheels  for  alignment,  play,  and  tighten  grease  plugs. 
Inspect  tires  for  cuts  and  see  that  rim  bolts  are  tight. 


CARE  AND  ADJUSTMENT  TABLES  339 

L.    Inspect  brake  bands  and  see  that  they  are  free  from  oil  and  do 

not  drag  on  the  drums. 

M.    Take  up  all  play  on  torsion  rod  springs. 
N.    Drain  radiator  and  refill  with  fresh  water.     See  that  fan  belt 

is  free  from  grease  and  has  proper  tension. 
O.    Pack  ball  joints  on  drag  link  with  grease. 

BI-WEEKLY  ATTENTION 

A.  On  the  Eiseman  Type  G  4  Edition  II,  Magneto,  20  drops  of  light 

oil  (3  in  1)  should  be  distributed  as  follows  (500  miles): 

1.  Oil  hole  on  breaker  box,  1  drop. 

2.  Small  hole  at  driving  end,  5  drops. 

3.  Large  hole  at  driving  end,  14  drops. 

B.  Inspect  transmission  and  subtransmission.     Level  in  transmis- 

sion should  be  just  above  top  of  countershaft.  If  below  add 
transmission  oil  to  bring  it  to  the  required  level.  Drain 
the  subtransmission  which  should  contain  six  quarts  of  trans- 
mission oil.  Add  enough  to  the  oil  drained  out  to  make  up 
the  six  quarts  and  replace.  Every  three  months  the  trans- 
mission and  subtransmission  should  be  drained,  washed  with 
kerosene,  and  refilled. 

C.  Fill  the  foot  brake  drum  with  grease  through  the  plug  in 

the  cap  on  the  rear  of  the  drum.  Remove  cap  and  clean 
bearings  every  three  months 

D.  Check  valve   clearance  adjusting  if  necessary   (intake   .004," 

exhaust  .006"). 

MONTHLY  ATTENTION 

A.  Examine  interrupter  points  on  magneto,  smoothing  and  ad- 

justing if  necessary.  Examine  control  connections  and  check 
timing  of  magneto. 

B.  Drain  carburetor,  gasoline  tank,  and  piping  to  remove  dirt  and 

water. 

C.  Drain  crank  case,  flush  with  kerosene,  remove  lower  half  of 

crank  case,  clean,  and  refill  with  six  quarts  of  cylinder  oil 
medium).  While  crank  case  is  off  inspect  bearings  for  loose- 
ness (1000  miles). 

D.  Put  four  ounces  of  cylinder  oil  (medium)  in  governor. 

E.  Repack  alignment  joint  with  grease. 


340  MOTOR  VEHICLES  AND  THEIR  ENGINES 

F.  Fill    front  and  rear    axle  housing  with  grease   through   plug 

holes.     Every  three  months,  drain  housing  wash  with  kerosene, 
and  refill  with  grease. 

G.  Fill  wheel  bearings  with  grease  through  plug  in  hub. 

H.    Lift  spring  retained  cover  on  top  of  steering  column  and  inject 

^  pint  of  transmission  oil. 

I.    Every  two  months  grease  the  spring  leaves  with  grease  and 
graphite. 

TABLE  5 

NASH  QUAD  TRUCKS 
DAILY  ATTENTION 

A.  The  crank  case  should  be  filled  with  cylinder  oil  (medium)  until 

the  indicator  rod  on  the  left  side  of  the  engine  reads  2)4  gal- 

B.  Turn  the  following  grease  cups  and  when  necessary  refill  with 

cup  grease: 

1.  Steering  knuckle  grease  cups. 

2.  Water  pump  grease  cups. 

3.  Clutch  grease  cups. 

C.  Put  a  few  drops  of  cylinder  oil   (medium)  in  the  following 

parts : 

1.  Spring  shackle  oil  holes. 

2.  Tie  rod  clevis  pins. 

3.  Clutch,  brake,  and  gear  shift  mechanism  oil  holes. 

4.  Motor  support  oil  holes. 

5.  Starting  crank  bearing  and  dog. 

D.  Every  second  day  fill  propeller  shaft  universal  joints  with  cup 

grease. 

E.  Wipe  off  magneto,  spark  plugs,  and  wiring. 

WEEKLY  ATTENTION 

A.  Clean  truck  thoroughly. 

B.  Clean  engine  and  running  gear  thoroughly. 

C.  Remove  spark  plugs,  clean  and  adjust  gaps,  and  replace.    Inspect 

and  clean  wiring  and  clean  distributor  plate  with  gasoline. 

D.  Run  the  engine  watching  for  oil  and  water  leaks,  unusual  sounds, 

and  loose  parts.     Examine  for  air  leaks  around  inlet  manifold 
and  carburetor. 


CARE  AND  ADJUSTMENT  TABLES  341 

E.  When  engine  is  hot  stop  and  test  for  compression  by  turning 

over  by  hand. 

F.  While  hot,  inject  a  tablespoonful  of  kerosene  in  each  cylinder 

through  the  pet  cock  and  allow  to  stand  over  night  to  loosen 
carbon. 

G.  Pack  the  following  parts  with  grease : 

1.  Fan  pulley  hub. 

2.  Drag  link  boots. 

3.  Steering  column  housing. 

4.  Axle  universal  joints. 

H.    Turn  the  steering  tube  grease  cups  and  refill  when  necessary 
with  cup  grease. 

I.    Oil  the  following  parts  with  cylinder  oil  (medium) : 

1.  Shifter  box  and  lever. 

2.  Hand  brake  shaft. 

3.  Brake  rocker  shafts  and  all  joints  on  brake  connections. 

4.  Transmission  support. 

5.  Steering  knuckle  brake  cam  studs. 

6.  Governor  drive  gears. 

7.  Governor  (fill  chamber  weekly  and  drain  monthly). 

J.    Tighten  spring  clip  nuts  and  inspect  springs  for  shifted  or 
broken  leaves. 

K.    Inspect  wheels  for  alignment  and  play.     Inspect  tires  for  cuts 
and  see  that  rim  bolts  are  tight 

L.    Inspect  brake  bands  and  see  that  they  are  free  from  oil  and  do 
not  drag  on  the  drums.     If  oily  wash  with  kerosene. 

M.    Drain  and  refill  radiator  with  fresh  water. 

BI-WEEKLY  ATTENTION 

A.  On.  the  Eiseman  Type  G  4  Edition  II  magneto,  20  drops  of  oil 

should  be  distributed  as  follows  (500  miles) : 

1.  Oil  hole  on  breaker  box,  1  drop. 

2.  Small  hole  on  driving  end,  5  drops. 

3.  Large  hole  on  driving  end,  14  drops. 

B.  Inspect  transmission  and  add  enough  transmission  oil  to  fill 

case  half  full  or  to  the  level  of  the  overflow  plug. 

C.  Fill  differential  housing  with  transmission  lubricant.     If  this  is 

too  heavy  in  winter  add  some  cylinder  oil  till  of  the  right 
consistency. 


342 


MOTOR  VEHICLES  AND  THEIR  ENGINES 


MONTHLY  ATTENTION 

A.  Examine  interrupter  points  on  magneto,  smoothing  and  ad- 

justing if  necessary.     Examine  control  connections  and  check 
timing  of  magneto. 

B.  Check  valve  clearance  and  adjust  if  necessary  (0.006"  on  inlet 

valves,  0.008"  on  exhaust). 

C.  Drain  carburetor,  gasoline  tank,  and  piping  to  remove  dirt  and 

water. 

D.  Drain  crank  case,  flush  with  kerosene,  and  refill  with  cylinder  oil. 

E.  Fill  wheel  bearings  with  grease  through  inner  plug  in  wheel 

housing. 

F.  Lubricate  internal  gears  in  wheels  through  outer  plugs  in  wheel 

housings  with  transmission  lubricant.     Do  not  put  in  too 
much  as  it  may  leak  out  on  the  brake  drums. 

G.  Every  two  months  grease  the  spring  leaves  with  grease  and 

graphite. 

TABLE  6 

SAMPLE  TABLE  OF  CARE  AND  ADJUSTMENT 
FOR  GARAGES 

DAILY 


8 

9 

10 

11 

12 

13 

1.  Gasoline  supply  

8  gal 

7  eal 

2.  Oil  level  crank  case 

1  pt 

x 

3.  Fill  up  with  water  

x 

x 

4.  Inspect  tires  for  proper  inflation 
5.  Springs  for  breakage  

X 

x 

X 

x 

6.  Lubricate  as  specified  by  man- 
ufacturers   

CARE  AND  ADJUSTMENT  TABLES 
WEEKLY 


343 


MAY 


8 


15 


22 


1.  Clean  apparatus  thoroughly X          X 

2.  Thoroughly  clean  engine  and  engine  compart- 

ment        X          X 

3.  Remove  spark  plugs,  clean  and  adjust  gap,  and 

replace X          X 

4.  Inspect  and  clean  wiring X          X 

5.  Clean  distributor  plate  with  gasoline X          X 

6.  With  engine  running  check  for. 

(a)  Water  leaks .' X  X 

(b)  Oil  leaks X  X 

(c)  Unusual  sounds X  X 

(d)  Loose  parts X  X 

(e)  Gasoline  line  leaks X  X 

(f)  Air  leaks  around  carburetor  and  intake.  X  X 

r   i  G    i  G 

7.  While  engine  is  hot,  test  compression  by  turn-  I     2  G      2  G 

ing  over  by  hand . .  .  1     3  G      3  F 

I    4  F      4  W 

8.  While  the  engine  is  still  hot  inject  a  tablespoon- 

ful  of  kerosene  in  each  cylinder  and  let  stand 

over  night  to  loosen  up  carbon X          X 

9.  Drain  radiator  and  refill  with  soft  water X          X 

10.  See  that  fan  belt  is  free  from  grease  and  has 

proper  tension X          X 

11.  Inspect  wheels  for  wheel  alignment  and  play.  .       X          X 

12.  Inspect  steering  apparatus X          X 

13.  Inspect  tires  for  cuts  and  see  if  rim  bolts  are 

tight X          X 

14.  Inspect  brake  bands  to  see  if  they  are  free  from 

oil  and  do  not  drag  on  drums;   see  if  they 

brake  equally X          X 

15.  Tighten  spring  clips  and  inspect  springs  for 

cracked,  broken,  or  shifted  spring  leaves ....      X          X 

16.  If  car  has  storage  battery,  test  specific  gravity 

in  each  cell.  If  the  reading  is  below  1.200 
the  battery  needs  attention.  After  testing 
fill  with  distilled  water  till  the  liquid  stands 
H  inch  above  plates X  X 


17.  Lubrication  as  specified  by  manufacturers 


344 


MOTOR  VEHICLES  AND  THEIR  ENGINES 
MONTHLY 


May 


June 


July 


Aug. 


1.  Check  valve  clearance  and  adjust X 

2.  Examine  interrupter  points  on  ignition  system.  X 

3.  Examine  control  connections. X 

4.  Check  timing  of  ignition X 

5.  Check   all   wiring   for   loose   connection    and 

chaffed  wires X 

6.  Drain  carburetor,  gasoline  tank,   and  piping 

to  remove  dirt  and  water X 

7.  Clean  cooling  system X 

8.  Test  for  play  in  wheel  bearings X 

9.  Test  for  play  in  differential X 

10.  Test  for  play  in  steering  apparatus X 

11.  Drain  crank  case,   clean  with  kerosene,   and 

refill  with  new  oil 6  qts 

12.  Lubricate  as  specified  by  manufacturers 


INDEX 


INDEX 


Page 

Accelerating  Well 68 

Air  Cooling 35 

Air  Cooled  Engine 35 

Air  Pressure  in  Tires 296 

Alcohol  as  Fuel 62 

Alcohol  Use  in  Radiator 46 

Alignment  of  Wheels 326 

Ampere,  Definition  of . . 129 

Anti-freezing  Mixtures 46 

Armature — 

Generator 210 

Magneto 172 

Atwater-Kent  Ignition  System ...  168 

Automatic  Spark  Advance 161 

Auxiliary  Air 67 

Auxiliary  Air  Valve 67 

Axles — 

Dead 273 

Live 273 

Axles,  Rear — 

Full  Floating 274 

Semi-Floating 275 

Three-quarter  Floating 275 


B 

Backfiring  in  Carburetors 304,  306 

Ball  Bearings 235 

Bar  Magnets 117 

Batteries — 

Dry 135 

Simple 135 

Storage 138 

Battery  Connections — 

Parallel 137 

Series 136 

Series-Parallel 137 

Battery  Ignition  Systems — 

Atwater-Kent. 168 

Delco 165 

Four-unit  Coil  (Ford) 159 

Northeast 161 

Reason  for 151 

Remy 168 

Simple 156 

Bearings — 

Ball 285 

Plain 285 

Roller 285 

Bendix  Drive 219 

Benzol  as  Fuel 61 

Berling  Magnetos 191 

Bevel  Gear  Drive 260 

Bever  Gear  Differential. .               .  265 


Page 

Bijur  Lighting  System 219 

Blow-out,  Tire 297 

Bosch  Magneto 182, 203 

Brake  Adjustments 280, 327 

Brake  Drums 279 

Brake  Equalizers 280 

Brake  Rods 280 

Brakes — 

External 279 

Internal 277 

Shaft 279 

Wheel 279 

Brake  Troubles 280 

Buick  Clutch. .  .  234 


CadUlac- 

Carburetor. . . , 83 

Cooling  System 40 

Firing  Order 30 

Pump 39 

Thermostat 39 

Calcium  Chloride,  Use  in  Radiator     47 

Camber 283 

Cannon  and  Engine  compared  ...       8 

Carbon  Monixide 67 

Carbon  Removal 319 

Carburetor — 

Adjustment  Precautions 67 

Definition  of 63 

Simple 64 

Carburetors — 

Cadillac 83 

Holley 114 

Hudson 91 

Kingston  Model  E 75 

Kingston  Model  Y 114 

Marvel 86 

Packard 76 

Peerless 78 

Pierce  Arrow 79 

Rayfield 104 

Schebler  Model  A  Special 106 

Schebler  Model  E 72 

Schebler  Model  H 73 

Stewart 89 

Stromberg  Model  G 81 

Stromberg  Model  M 93 

White 109 

Zenith 99 

Carburetion,  Principles  of 63 

Care  and  Adjustment  Tables — 

Dodge 331 

Ford 334 

F.  W.  D. .  .  337 


347 


348 


INDEX 


Page 

Care  of  Gasoline 54 

Casings,  Tire 291 

Caster  Effect 283 

Cells  (see  Batteries). 

Centrifugal  Pump 44 

Chain  Drive 258 

Charging  Storage  Batteries 143 

Chemical  Reaction  in  Storage  Bat- 
tery    140 

Chokes 69 

Circuit  Breaker 218 

Clincher  Tires 291 

Clutch  Adjustment 326 

ClutchBrake 232 

Clutch,  Object  of 232 

Clutch  Requirements 232 

Clutch  Troubles 240 

Coils- 
Induction 151 

Vibrating 149 

Cold  Test  for  Oils 310 

Combustion  of  Fuel 1 

Combustion  of  Gasoline — 

Lower  Limit 63 

Upper  Limit 63 

Commutator 209 

Compound  Wound  Machines 212 

Compression  Leaks 317 

Condensers  for  Cooling  Systems.  .  41 

Condensers  for  Ignition 150 

Conductors 131 

Cone  Clutch 233 

Cooling  Losses 5 

Pooling  Systems 34 

Cooling  System,  Cleaning 321 

Cord  Tires 289 

Counter  Balancing  of  Parts 21 

Counter  Balance  Weights 22 

Crank  Case,  Cleaning 314 

Crude  Oil  as  Fuel. 55 

Crude  Oil,  Composition  of 55 

Cup  Grease 311 

Cut  Out,  Magnetic 214 

Cycle  of  an  Engine 8 


Delco  Ignition  System 165 

Delco  Starting  and  Lighting  System  222 

Diesel  Engine 1 

Differential  Lock 268 

Differential,  Object  of 263 

Differential,  Operation  of 263 

Differential  Reduction 260 

Direct  Current  Machines 207 

Distance  Rods 262 

Distilled  Water,  Use 143 

Distillation  of  Crude  Oil 56 

Distributors 154,  324 

Distributor,  Speed  of 155 

Dixie  Magneto .  197 


Page 

Dodge- 
Care  and  Adjustment  Table. .   331 

Drive  Shaft 259 

Firing  Order 25 

Fuel  Feed  System 50 

Ignition  Syst  m 161 

Steering  Apparatus 284 

Timing... 18 

Transmission 248 

Drag  Link 282 

Draining  Radiator 46 

Drive,  How  to 299 

Drive  Shafts 259 

Dry  Cell,  Composition  of 136 

Dual  Ignition 201 

Dunlop  Tires 291 


E 


Efficiency- 
Mechanical  . 
Thermal. . 


6 

7 

Eight  Cylinder  Engine 28 

Eisemann  Magneto 188 

Electrical  Circuits 132 

Electrical  Lag 152 

Electrical  Resistance 131 

Electrical  Symbols 134 

Electricity 128 

Electrolyte 138 

Electro-Magnetic  Induction 146 

Engine  Balance 21 

Engine  Horse  Power 6 

Engine  Knock 304, 306 

Engine  Lacks  Power 304, 307 

Engine  Misses 303,  305 

Engine  Nomenclature 2 

Engine  Overheats 304,  307 

Engine  Timing,  Average 19 

Engine  Troubles 303 

Engine  Won't  Stop 305,  308 

Expansion  Due  to  Heat 1 


Fans 45 

Faraday's  Law 175 

Field  Windings 210 

Fire  Point  for  Oils 310 

Firing  Orders — 

Cadillac 30 

Dodge 25 

Ford 25 

Four-wheeled  Tractor 25 

F.  W.  D 25 

Holt 25 

Nash 25 

Packard 25 

Packard  12 30 

Standardized  B 25 

White..                                    ...  25 


INDEX 


349 


Page 
Firing  Orders,  Possible — 

Four  Cylinder 25 

Six  Cylinder 28 

Flash  Point  of  Oils 310 

Flexible  Couplings 178 

Float  Chambers 64,  70 

Flooding  Carburetor 69 

Fly-wheel,  Reason  for. ; 30 

Force  Cooling  System 37 

Ford- 
Bevel  Gear  Drive 260 

Care  and  Adjustment  Table. . .  334 

Commutator  Timing 326 

Cooling  System 37 

Differential 265 

Firing  Order 25 

Ignition  Wiring 169 

Magneto 225 

Transmission 253 

Four  Cycle  Engine 13 

Four  Cycle  Engine  Operation ....     10 

Four  Cylinder  Engine 25 

Four  Unit  Coil  Ignition  System .  .    159 
Four-wheel  Tractor  Firing  Order.  .     25 

Frames 270 

Freezing  of  Storage  Batteries 144 

Friction  Transmission 243 

Front  Axles 273 

Fuel  Feed  Systems 48,  322 

Fuel  Oil 56 

Fuels 55 

F.  W.  D.— 

Care  and  Adjustment  Table .  .  337 

Firing  Order 25 

Timing 18 

Transmission. .  .251 


Gas  Engine 1 

Gasoline  as  Fuel 58 

Gasoline  Fire,  How  Extinguished.  54 

Gather 283 

Gear  Grease 316 

Gear  Ratio 243 

Gear  Reduction 243 

Gear  Rotation 242 

Gear  Shift  Mechanism 248 

Generator  Armature 210 

Generator,  Charging  Rate 214 

Generator,  Principle  of 208 

Generator  Regulation 215 

Glycerine,  Use  in  Radiator 47 

Governors ; 71 

Gravity  Fuel  Feed  System 48 

Grids,  Storage  Battery 138 


Heat  Energy  Diagram 5 

Hete-Shaw  Clutch..  .  236 


Page 

Helical  Gear  Drive 261 

High  Tension  Magnetos 178, 196 

Holly  Carburetor 114 

Holt— 

FiringOrder 25 

Radiator 44 

Timing 18 

Horse  Power — 

Brake 6 

Formulae 6 

Indicated 7 

Hotchkiss  Drive 262 

How  to  Drive 299 

Hudson  Carburetor 91 

Hydrometer 141 


I 


Ignition  Timing 21, 325 

Impulse  Starter 177 

Indian  Motorcycle  Transmission.  246 

Induction,  Laws  of 147 

Induction  Coil,  Vibrating 158 

Inertia,  Gasoline 68 

Inner  Tubes 292 

Insulators 131 

Interrupter,  Gap  at  Points  of. ...  154 


K 


Kerosene  as  Fuel 61 

Kerosene  in  Cooling  System 47 

King  Pin 282 

Kingston  Carburetors 75, 114 

Knocks,  Engine 304,  306 

K.  W.  Magneto 196 


Laws  of  Induction 147 

Laws  of  Magnets 122 

Lean  Mixture 64 

Leese-Neville  System 218 

Loadstone 117 

Low  Tension  Magnetos. .  .  178, 196,  201 
Lubricants — 

Specifications  of 310 

Cold  Point 310 

Fire  Point 310 

Flash  Point 310 

Specific  Gravity 310 

Viscosity 310 

Lubricating  Systems — 

Force  Feed 313 

Force  Feed  with  Splash 312 

Full  Force  Feed 313 

Splash 311 

Splash  with  Circulating  Pump.  312 


350 


INDEX 


Page 

Lubrication,  Object  of 309 

Lubrication  of  Clutch 314 

Lubrication  of  Engine 3 

Lubrication  of  Joints 314 

Lubrication  of  Magneto 324 

Lubrication  Troubles 314 


M 

Magnetic  Induction 122 

Magnetic  Field,  Resultant 120 

Magnetic  Fields — 

About  Bar  Magnet 118 

About  Current  Carrying  Con- 
ductor    124 

About  an  Electro-Magnet 126 

About  a  Helix 125 

About  Horse  Shoe  Magnet. ...   119 

About  a  Loop  of  Wire 125 

About  Solenoid 125 

Magnetic  Leakage 117 

Magnetic  Substance 117 

Magnetic  Whirls 124 

Magnetism,  Definition  of 117 

Magneto  and  Battery  Systems — 

Bosch  Dual 203 

Remy  Dual 201 

Vibrating  Duplex 205 

Magneto  Lubrication 324 

Magneto,  Principle  of  Operation — 

Armature  Type 172 

Rotor  Type 193 

Magneto,  Typical  Construction ...   179 
Magnetos — 

BerlingB21 192 

BerlingF41 191 

Bosch  Du4 182 

Bosch  LT4 186 

Bosch  ZEV 186 

Bosch  ZR4 185 

Dixie 197 

Eisemann 188 

Ford 225 

K-W 196 

Remy 193,201 

Magnets — 

Effect  of  Heat 123 

Effect  of  Vibration 123 

Electro 126 

Permanent 117 

M.  and  S.  Differentials 267 

Marking  of  Fly  Wheel 19 

Marking  of  Timing  Gear 19 

Marvel  Carburetor 86 

Master  Vibrator 160 

Mechanical  Advantage  of  Gears.  .  241 

Mechanical  Balance 21 

Method  of  Drive 259 

Mixture,  Lean,  Perfect  or  Rich ...     64 

Molecular  Theory 122 

Motor,  Electric 212 

Motor-cycle  Magnetos 179 


Motor-generator — 

Effect  of  Speed  on 214 

Rotation 213 

Motor,  Principle  of 212 

Motor  Rule 213 

Mufflers 286 

Multiple  Disc  Clutch 240 

Multi-cylinder  Engine,  Advantages     30 
Mutual  Induction 148 


N 
Nash — • 

Care  and  Adjustment  Table.  .   340 

Clutch 239 

Firing  Order 25 

Transmission 251 

Needle  Valves 66 

Negative  Plates,  Composition  of.  .   138 

Non-Megnetic  Substances 117 

Non-saturated    Coil    (also    see 

Timers) 154 

Northeast  Ignition  System 161 

Northeast  Starting  and  Lighting 

System 215 


Offset  Cylinders 

Ohm,  Definition  of 

Ohm's  Law 

Oil  (see  Lubricants). 

One  Cylinder  Engine 

Over-heated  Engine,  Effect  of. 


20 
129 
130 

21 
34 


Packard — 

Carburetor 76 

Clutch 236 

Cooling  System 41 

Firing  Order 25,30 

Packing  Water  Pump  Glands 321 

Peerless  Carburetor 78 

Permeability 119 

Pet  Cocks 69 

Pierce- Arrow  Carburetor 79 

Pitman  Arm 282 

Plain  Bearings 285 

Planitary  Transmission 253 

Plate  Clutch 237 

Plates  for  Storage  Battery 138 

Pneumatic  Tires 289 

Pocketed  Spark  Plugs 158 

.Polarity 117 

Positive  Plates,  Composition 138 

Power  Balance 21 

Power  Overlap 33 

Power  Transmission  Units 227 

Pressure  Fuel  Feed  System 49 

Pressure,  for  Tires 296 


INDEX 


351 


Page 

Pressure  Gauge 49 

Pressure  Pump,  Gasoline 49 

Primary  Air 65 

Priming 69,315 

Progressive  Gear  Transmission .  .  .  244- 
Puddle  Type  Carburetor 114 

Pumps — 

Centrifugal 44 

Gear. .  43 


Quick  Detachable  Tires 294 


Radiators — 

Cellular 45 

Honey-comb 44 

Tubular 44 

Radius  Rods 262 

Rate  of  Flame  Propagation 64 

Rayfield  Carburetor 104 

Rear  Axles 274 

Remy  Ignition  System 168 

Remy  Magneto 193,  201 

Residual  Magnetism 210 

Reversing  Switch,  Ignition 163 

Rich  Mixtures 64 

Right-hand  Rule  for  Magnetism. .    126 
Right-hand  Rule  for  Induction.  .  .   147 

Rims 289 

Road  Inspection 330 

Rock  of  the  Piston 17 

Roller  Bearings 285 

Running  Gear 270 


Safety  Spark  Gap 185 

Saturated  Coil 154 

Schebler  Carburetors 91,  106 

Secondary  Air 67 

Selective  Gear  Transmission 246 

Self-Induction 148 

Series  Wound  Machine 211 

Shaft  Drive 258 

Shunt  Wound  Machine 211 

Six  Cylinder  Engine 26 

Skidding 302 

Spark  Plugs 156 

Spark  Plug  Gap 157 

Spark  Plug  Location 157 

Spark  Plug  Threads 157 

Spark  Plug  Troubles 323 

Specific  Gravity,  Storage  Battery.  141 

Spray  Nozzle 64 

Spring  Clips 273 

Spring  Saddle  Clips 271,  328 

Spring  Shackles 271 


Page 

Springs — 

Cantilever 272 

Full  Elliptic 272 

Platform 272 

Three-quarters  Elliptic 272 

Semi-Elliptic 272 

Springs,  Care  of 328 

Spur  Gear  Differential 266 

Standardized  B — 

Firing  Order 25 

Starting  and  Lighting  Systems — 

Bijur 220 

Detco 222 

Ford 225 

Leese-Neville 218 

Northeast 215 

Steering  Apparatus 282 

Steering  Gear — 

Irreversible 284 

Reversible 284 

Steering  Gear  Adjustment 327 

Steering,  How  Accomplished 281 

Steering  Knuckle 282 

Stewart  Carburetor 89 

Stewart  Vacuum  System 51 

Storage  Battery  Charging  Board .  .    145 
Storage  Batteries — 

Care  of 143 

Charging 143 

To  Put  in  Operation 142 

Strokes  of  a  Four-cycle  Engine — 

Compression 10 

Exhaust 10 

Suction 10 

Power 10 

Stromberg  Carburetors 81,  93 

Sub-frame 270 

Suction,  effect  of 65 


Temperature  for  Cooling  Water .  .  34 

Thawing  Out  Engine. 47 

Thermo-Syphon  Cooling  System . .  35 
Thermostatic  Controlled  Cooling 

System 39 

Thermostat 39 

Third  Differential 269 

Threads,  Spark  Plug 157 

Three-point  Suspension 270 

Three-cylinder  Engine 26 

Throttle 65 

Thrust  Bearing 286 

Tie  Rod 282 

Timer  Control 154 

Timer-Distributor 155 

Timers 152 

Timer  Speed 153 

Tire  Casing 289 

Tire  Chains 293 

Tire  Construction. .                        .  289 


352 


INDEX 


Tires- 
Pneumatic 289 

Solid 293 

Tires,  Care  and  Attention 296 

Tires,  Troubles  and  Repairs. .       .  297 

Toe  in  on  Wheels 326 

Torque  Arms 262 

Torque  Tubes 262 

Transmission — 

Object  of 241 

Types 244 

Twelve  Cylinder  Engine 30 

Two-cycle  Engine — 

Advantages 13 

Disadvantages 13 

Two  Port 11 

Three  Port 12 

Two-cylinder  Engine — 

Vertical  180°. .  23 

Vertical  360° 23 


Unisparker 168 

Universal  Joints 258 


Vacuum  Fuel  Feed  System 51 

Valve  Clearance 318 

Valve  Grinding 318 

Valve  Tappet  Adjustment 318 


Page 
Valve  Timing — 

Exhaust 16 

Inlet 14 

Valves,  Inner  Tubes 292 

Vaporization  of  Liquids 69 

Venturi  Tube 65 

Vibrators 149 

Viscosity  of  Oils 310 

Volt,  Definition  of 129 

Voltage — 

Of  Dry  Cells 136 

Of  Storage  Cells 138 


W 

Water  Analogy  for  Current  Flow  1 28 , 1 32 

Wheel  Alignment 326 

Wheels- 
Steel 277 

Wire 277 

Wood 276 

White- 
Carburetor  109 

Clutch 239 

Firing  Order 25 

Timing 18 

Transmission 250 

Wiring  Inspection 323 

Worm  Drive 261 

Worm  Gear  Differential . .  .  266 


Zenith  Carburetor. . 99 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 
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